tag:theconversation.com,2011:/global/topics/milky-way-106/articlesMilky Way – The Conversation2024-01-02T16:49:57Ztag:theconversation.com,2011:article/2195462024-01-02T16:49:57Z2024-01-02T16:49:57ZPrivatised Moon landings: the two US missions set to open a new era of commercial lunar exploration<figure><img src="https://images.theconversation.com/files/566549/original/file-20231219-23-qde9s6.jpeg?ixlib=rb-1.1.0&rect=0%2C2%2C1839%2C984&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://svs.gsfc.nasa.gov/10836">Photograph: Nasa (Goddard Space Flight Center)</a></span></figcaption></figure><p>Two commercial spacecraft are scheduled to launch to the Moon early in 2024 under a Nasa initiative called the Commercial Lunar Payload Service <a href="https://www.nasa.gov/commercial-lunar-payload-services/">CLPS</a>. This programme is intended to kickstart a commercial transportation service that can deliver Nasa experiments and other payloads to the lunar surface.</p>
<p>If successful, these missions will represent the first landings on the Moon by spacecraft designed and flown by private companies. They could potentially open up a new era of commercial lunar exploration and science. </p>
<p>CLPS was inaugurated by Nasa in 2018. An initial pool of nine companies received an invitation to join the programme. They included <a href="https://www.astrobotic.com/">Astrobotic</a> and <a href="https://www.intuitivemachines.com/">Intuitive Machines</a>, the two companies behind these missions. Both missions expect to land within a week after lift-off.</p>
<p>The first launch, and the first Nasa flight of 2024, is the Peregrine lunar lander, built by Pittsburgh-based Astrobotic. It is scheduled to launch at the earliest on January 8. Broadly speaking, the lander is a box the size of a medium-sized garden shed containing several separate experiments. </p>
<p>These include a set of mirrors called a laser retro-reflector array, used for accurate positioning of the lander from orbit. There are also a number of spectrometers – instruments that separate and measure the distinct colours found in light. These will measure radiation on the lunar surface and look for signatures of water in lunar soil.</p>
<p>One of them, the <a href="https://nssdc.gsfc.nasa.gov/nmc/experiment/display.action?id=PEREGRN-1-02">Neutron Spectrometer System</a>, will look for hydrogen-containing materials on the surface, which can indicate the presence of water below ground. This water could one day be used by human explorers.</p>
<figure class="align-center ">
<img alt="Astrobotic Peregrine lander." src="https://images.theconversation.com/files/566548/original/file-20231219-19-i3ffem.jpeg?ixlib=rb-1.1.0&rect=0%2C0%2C1917%2C1279&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/566548/original/file-20231219-19-i3ffem.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/566548/original/file-20231219-19-i3ffem.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/566548/original/file-20231219-19-i3ffem.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/566548/original/file-20231219-19-i3ffem.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/566548/original/file-20231219-19-i3ffem.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/566548/original/file-20231219-19-i3ffem.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Astrobotic’s Peregrine lander will touch down near the Gruithuisen Domes.</span>
<span class="attribution"><a class="source" href="https://images.nasa.gov/details/KSC-20231114-PH-ILW01_0100">Isaac Watson/Nasa</a></span>
</figcaption>
</figure>
<p>There are two principle sources of dangerous radiation for humans in space. One is the Sun, which unleashes electrons, protons and heavier ions that are accelerated to a significant fraction of the speed of light. </p>
<p>These solar energetic particle events (SEPs) are more likely to occur during the Sun’s peak of activity (solar maximum), which occurs every 11 years. However, that does not mean there is a respite during the solar minimum.</p>
<p>The other source of harmful radiation is galactic cosmic rays (GCRs). These energetic particles originate outside the Solar System, probably in explosive phenomena such as exploding stars (supernovas).</p>
<p>During periods of lower solar activity (including the solar minimum), the Sun’s magnetic field, which extends throughout the Solar System, weakens. This enables <a href="https://www.researchgate.net/figure/Solar-cycle-%20modulation-and-anti-correlation-of-GCR-flux-with-solar-activity-Shown-are_fig6_257343697">more GCRs</a> to reach us instead. </p>
<p>Another spectrometer on Peregrine will measure both SEPs and GCRs on the Moon. This is important for examining how dangerous the radiation environment at the lunar surface will be for future human explorers.</p>
<h2>Polar landing</h2>
<p>The second spacecraft to launch early in 2024 is the <a href="https://www.intuitivemachines.com/im-1">Nova-C lander</a>. It is designed by Houston-based Intuitive Machines and has a similar volume to Peregrine, but in the shape of a tall, hexagonal cylinder. It will carry several instruments including its own laser retro-reflector array. Nova-C is currently scheduled to launch in mid-February.</p>
<p>Other instruments include a suite of cameras for producing a 3D image of Nova-C’s landing site. This will allow scientists to estimate how much material is blown away by the landing rocket’s exhaust plume during the descent. Potentially, any material blown away can be imaged to get an idea of the composition of surface material. </p>
<figure class="align-center ">
<img alt="Nova-C lander." src="https://images.theconversation.com/files/566583/original/file-20231219-23-2hpa5p.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/566583/original/file-20231219-23-2hpa5p.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/566583/original/file-20231219-23-2hpa5p.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/566583/original/file-20231219-23-2hpa5p.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/566583/original/file-20231219-23-2hpa5p.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/566583/original/file-20231219-23-2hpa5p.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/566583/original/file-20231219-23-2hpa5p.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A model of the Nova-C lander.</span>
<span class="attribution"><a class="source" href="https://images.nasa.gov/details/NHQ201905310022">Nasa (Goddard Space Flight Center)</a></span>
</figcaption>
</figure>
<p>The “radio observations of the lunar surface photo-electron sheath” (<a href="https://arxiv.org/pdf/2102.02331.pdf">Rolses</a>) instrument is designed to measure how the extremely tenuous lunar atmosphere and the Moon’s surface dust environment affect radio waves. </p>
<p>The behaviour of electrically charged dust particles on the Moon is a technical challenge which future explorers will need to deal with, as the abrasive particles can attach themselves to surfaces and mechanical devices and potentially cause harm if <a href="https://www.wired.com/story/the-%20next-big-challenge-for-lunar-astronauts-moon-dust/">inhaled</a> by astronauts.</p>
<p>A privately built experiment onboard Nova-C is the International Lunar Observatory <a href="https://iloa.org/ilo-x-precursor/">ILO-X</a>, which will aim to capture some of the first images of the Milky Way galaxy from the Moon’s surface. This would demonstrate the concept of lunar-based astronomy.</p>
<h2>Landing locations</h2>
<p>Peregrine’s landing site is a bay on the west side of Mare Imbrium, known as Sinus Viscositatis (Bay of Stickiness). Here, two volcanic mountains called the <a href="https://moon.nasa.gov/resources/482/a-lunar-%20mystery-the-gruithuisen-domes/">Gruithuisen Domes</a> are made of a different material to the surrounding plains. </p>
<p>The plains are a form of basalt, while the domes are composed of silica. Both are volcanic in origin, but one appears to have been formed by lava with a viscosity of mango chutney (the silica), and the other by runnier lava (the basalt). </p>
<figure class="align-center ">
<img alt="Gruithuisen Domes" src="https://images.theconversation.com/files/566614/original/file-20231219-29-7x7oaq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/566614/original/file-20231219-29-7x7oaq.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/566614/original/file-20231219-29-7x7oaq.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/566614/original/file-20231219-29-7x7oaq.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/566614/original/file-20231219-29-7x7oaq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/566614/original/file-20231219-29-7x7oaq.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/566614/original/file-20231219-29-7x7oaq.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Gruithuisen Domes appear to have been formed by silica lavas.</span>
<span class="attribution"><a class="source" href="https://moon.nasa.gov/resources/482/a-lunar-mystery-the-gruithuisen-domes/">Nasa (GSFC)/Arizona State University</a></span>
</figcaption>
</figure>
<p>On Earth, silica lavas typically require the presence both of water and plate tectonics. However, plate tectonics are not known to be present on the Moon, and neither is water in the quantities necessary for silica lavas. The Gruithuisen Domes thus present a geological enigma which Peregrine could go some way to resolving.</p>
<p>The landing location for Nova-C is Malapert A crater – which is of particular interest for lunar exploration, as it lies close to the Moon’s south pole. The surrounding mountains permanently shield this depression from sunlight, leaving it in constant darkness. </p>
<p>Consequently, it is one of the coldest locations in the Solar System and, given the lack of sunlight, a place where water ice delivered by comets hitting the surface over the aeons could remain stable. Future human explorers could use it for life support and making rocket fuel.</p>
<figure class="align-center ">
<img alt="Lunar south pole." src="https://images.theconversation.com/files/566615/original/file-20231219-27-888tuc.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/566615/original/file-20231219-27-888tuc.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/566615/original/file-20231219-27-888tuc.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/566615/original/file-20231219-27-888tuc.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/566615/original/file-20231219-27-888tuc.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/566615/original/file-20231219-27-888tuc.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/566615/original/file-20231219-27-888tuc.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">An image of the Moon’s South Pole showing the Malapert crater (foreground).</span>
<span class="attribution"><a class="source" href="https://svs.gsfc.nasa.gov/5127">Nasa's Scientific Visualization Studio</a></span>
</figcaption>
</figure>
<p>There are additional payloads on both spacecraft from private investors. Peregrine contains the “DHL Spacebox”, which will carry personal items from paying customers, while Nova-C contains “The Humanity Hall of Fame” – a list of names to be sent to the Moon for posterity. Such payloads can generate additional funding for the launch companies.</p>
<p>Several other companies are due to launch their first payloads to the Moon in the next couple of years. With greater input from private companies – assuming the these first few missions succeed – we may soon witness a new era in lunar exploration.</p><img src="https://counter.theconversation.com/content/219546/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The Peregrine and Nova-C landers are due to carry out valuable science at two diverse lunar locations.Gareth Dorrian, Post Doctoral Research Fellow in Space Science, University of BirminghamIan Whittaker, Senior Lecturer in Physics, Nottingham Trent UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1930712023-07-31T12:23:25Z2023-07-31T12:23:25ZWhat happens if someone dies in space?<figure><img src="https://images.theconversation.com/files/516818/original/file-20230321-2335-y7uosd.jpg?ixlib=rb-1.1.0&rect=22%2C0%2C4970%2C3000&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">An artist's depiction of two astronauts on Mars. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/astronauts-exploring-mars-royalty-free-image/1318550764?phrase=astronauts%20on%20Mars&adppopup=true">cokada/E+ via Getty Images</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
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<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
<hr>
<blockquote>
<p><strong>What happens if someone dies in space? – Guillermo, Palm Beach, Florida</strong></p>
</blockquote>
<hr>
<p>There’s no question that sending human beings to space is an extraordinarily difficult and perilous proposition. </p>
<p>Since human space exploration began just over 60 years ago, 20 people have died – 14 in the <a href="https://www.nasa.gov/feature/35-years-ago-remembering-challenger-and-her-crew">NASA space shuttle tragedies of 1986</a> and <a href="https://www.npr.org/2023/02/01/1153150931/columbia-space-shuttle-disaster-20th-anniversary">2003</a>, three cosmonauts during <a href="https://www.nasa.gov/feature/50-years-ago-remembering-the-crew-of-soyuz-11">the 1971 Soyuz 11 mission</a>, and three astronauts in the <a href="https://www.nasa.gov/feature/55-years-ago-tragedy-on-the-launch-pad">Apollo 1 launch pad fire in 1967</a>.</p>
<p>Given how complicated human spaceflight is, it’s actually remarkable how few people have lost their lives so far. But NASA plans to send <a href="https://www.nasa.gov/feature/artemis-iii">a crew to the Moon in 2025</a> and astronauts to Mars <a href="https://www.nasa.gov/directorates/spacetech/6_Technologies_NASA_is_Advancing_to_Send_Humans_to_Mars">in the next decade</a>. Commercial spaceflight <a href="https://www.nasa.gov/directorates/spacetech/6_Technologies_NASA_is_Advancing_to_Send_Humans_to_Mars">is becoming routine</a>. As space travel becomes more common, so does the possibility that someone might die along the way. </p>
<p>It brings to mind a gloomy but necessary question to ask: If someone dies in space – what happens to the body?</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/516825/original/file-20230321-26-l9gw62.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An artist's concept of an astronaut on Mars, sitting against a rock and gazing at the space colony sitting in the distance on dusty orange flatland." src="https://images.theconversation.com/files/516825/original/file-20230321-26-l9gw62.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/516825/original/file-20230321-26-l9gw62.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/516825/original/file-20230321-26-l9gw62.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/516825/original/file-20230321-26-l9gw62.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/516825/original/file-20230321-26-l9gw62.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/516825/original/file-20230321-26-l9gw62.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/516825/original/file-20230321-26-l9gw62.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">In the future, NASA and other space agencies, along with private industry, hope to establish colonies on Mars.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/astronaut-on-planet-mars-watching-a-space-station-royalty-free-image/1398989851">janiecbros/E! via Getty Images</a></span>
</figcaption>
</figure>
<h2>Death on the Moon and Mars</h2>
<p>As <a href="https://www.bcm.edu/people-search/emmanuel-urquieta-ordonez-32141">a space medical doctor</a> who works to find new ways to keep astronauts healthy, I and my team at the <a href="https://www.bcm.edu/academic-centers/space-medicine/translational-research-institute">Translational Research Institute for Space Health</a> want to make sure space explorers are as healthy as they can be for space missions.</p>
<p>Here is how death in space would be handled today: If someone died on a low-Earth-orbit mission – such as aboard the <a href="https://www.nasa.gov/mission_pages/station/main/index.html">International Space Station</a> – the crew could return the body to Earth in a capsule within a matter of hours. </p>
<p>If it happened on the Moon, the crew could return home with the body in just a few days. NASA already has detailed <a href="https://www.nasa.gov/sites/default/files/atoms/files/ochmo-tb-012_mortality_related_to_human_spaceflight.pdf">protocols in place for such events</a>. </p>
<p>Because of that quick return, it’s likely that preservation of the body would not be NASA’s major concern; instead, the No. 1 priority would be making sure the remaining crew returns safely to Earth. </p>
<p>Things would be different if an astronaut died during the <a href="https://nineplanets.org/questions/how-long-does-it-take-to-get-to-mars/">300 million-mile trip to Mars</a>. </p>
<p>In that scenario, the crew probably wouldn’t be able to turn around and go back. Instead, the body would likely return to Earth along with the crew at the end of the mission, which would be a couple of years later. </p>
<p>In the meantime, the crew would presumably preserve the body in a separate chamber <a href="https://doi.org/10.3357/AMHP.6146.2023">or specialized body bag</a>. The steady temperature and humidity inside the space vehicle would theoretically help preserve the body. </p>
<p>But all those scenarios would apply only if someone died in a pressurized environment, like a space station or a spacecraft. </p>
<p>What would happen if someone stepped outside into space <a href="https://www.livescience.com/human-body-no-spacesuit">without the protection of a spacesuit</a>? </p>
<p>The astronaut would die almost instantly. The loss of pressure and the exposure to the vacuum of space would make it impossible for the astronaut to breathe, and blood and other body fluids would boil. </p>
<p>What would happen if an astronaut stepped out onto the Moon or Mars without a spacesuit? </p>
<p>The Moon has nearly no atmosphere – <a href="https://www.nasa.gov/mission_pages/LADEE/news/lunar-atmosphere.html">a very tiny amount</a>. Mars has <a href="https://solarsystem.nasa.gov/planets/mars/overview/#:%7E">a very thin atmosphere</a>, and almost no oxygen. So the result would be about the same as exposure to open space: suffocation and boiling blood.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/8yU33cguGaY?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Radiation exposure, toxic soil and leaky spacesuits are three of the ways to die on Mars.</span></figcaption>
</figure>
<h2>What about burial?</h2>
<p>Suppose the astronaut died after landing, while on the surface of Mars. </p>
<p>Cremation isn’t desirable; it requires too much energy that the surviving crew needs for other purposes. And burial isn’t a good idea, either. Bacteria and other organisms from the body could <a href="https://theconversation.com/colonizing-mars-means-contaminating-mars-and-never-knowing-for-sure-if-it-had-its-own-native-life-103053">contaminate the Martian surface</a>. Instead, the crew would likely preserve the body in a specialized body bag until it could be returned to Earth. </p>
<p>There are still many unknowns about how explorers would deal with a death. It’s not just the question of what to do with the body. Helping the crew deal with the loss, and helping the grieving families back on Earth, are just as important as handling the remains of the person who died. But to truly colonize other worlds – whether the Moon, Mars or a planet outside our solar system – this grim scenario will require planning and protocols.</p>
<hr>
<p><em>Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>. Please tell us your name, age and the city where you live.</em></p>
<p><em>And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.</em></p><img src="https://counter.theconversation.com/content/193071/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Emmanuel Urquieta is supported by the Translational Research Institute for Space Health.</span></em></p>If an astronaut were to die on Mars, neither cremation nor burial would be good options.Emmanuel Urquieta, Professor of Space Medicine and Emergency Medicine, Baylor College of Medicine Licensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2088792023-06-30T16:33:17Z2023-06-30T16:33:17ZFirst ever view of the Milky Way seen through the lens of neutrino particles<figure><img src="https://images.theconversation.com/files/535016/original/file-20230630-29-2zlq8e.jpg?ixlib=rb-1.1.0&rect=39%2C9%2C6557%2C3712&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Milky Way, as seen with neutrino particles.</span> <span class="attribution"><a class="source" href="https://icecube.wisc.edu/gallery/high-energy-neutrinos-from-the-galactic-plane/#modulagallery-10913-11962">IceCube Collaboration / US National Science Foundation (Lily Le and Shawn Johnson) / ESO (S. Brunier)</a></span></figcaption></figure><p>Data collected by an observatory in Antarctica has produced our first view of the Milky Way galaxy through the lens of neutrino particles. It’s the first time we have seen our galaxy “painted” with a particle, rather than in different wavelengths of light.</p>
<p>The result, <a href="https://www.science.org/doi/10.1126/science.adc9818">published in Science</a>, provides researchers with a new window on the cosmos. The neutrinos are thought to be produced, in part, by high-energy, charged particles called cosmic rays colliding with other matter. Because of the limits of our detection equipment, there’s much we still don’t know about cosmic rays. Therefore, neutrinos are another way of studying them. </p>
<p>It has been speculated since antiquity that the Milky Way we see arching across the night sky consists of stars like our Sun. In the 18th century, it was recognised to be a flattened slab of stars that we are viewing from within. It is only 100 years since we learnt that the Milky Way is in fact a galaxy, or “island universe”, one among a hundred billion others.</p>
<p>In 1923, the American astronomer <a href="https://www.nasa.gov/content/about-story-edwin-hubble">Edwin Hubble</a> identified a type of pulsating star called a “Cepheid variable” in what was then known as the Andromeda “nebula” (a giant cloud of dust and gas). Thanks to the prior work of Henrietta Swan Leavitt, this provided a measure of the distance from Earth to Andromeda. </p>
<p>This demonstrated that Andromeda is a far away galaxy like our own, settling a long-running debate and completely transforming our notion of our place in the universe.</p>
<h2>Opening windows</h2>
<p>Subsequently, as new astronomical windows have opened on to the sky, we have seen our galactic home in many different wavelengths of light –- in radio waves, in various infrared bands, in X-rays and in gamma-rays. Now, we can see our cosmic abode in neutrino particles, which have very low mass and only interact very weakly with other matter – hence their nickname of “ghost particles”. </p>
<p>Neutrinos are emitted from our galaxy when cosmic rays collide with interstellar matter. However, neutrinos are also produced by stars like the Sun, some exploding stars, or supernovas, and probably by most high-energy phenomena that we observe in the universe such as gamma-ray bursts and quasars. Hence, they can provide us an unprecedented view of highly energetic processes in our galaxy – a view that we can’t get from using light alone.</p>
<figure class="align-center ">
<img alt="Digital Operating Module." src="https://images.theconversation.com/files/535040/original/file-20230630-21-lpttam.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/535040/original/file-20230630-21-lpttam.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/535040/original/file-20230630-21-lpttam.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/535040/original/file-20230630-21-lpttam.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/535040/original/file-20230630-21-lpttam.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/535040/original/file-20230630-21-lpttam.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/535040/original/file-20230630-21-lpttam.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A digital operating module, part of the IceCube observatory, being lowered into the ice.</span>
<span class="attribution"><a class="source" href="https://icecube.wisc.edu/gallery/high-energy-neutrinos-from-the-galactic-plane/#modulagallery-10913-2055">Mark Krasberg, IceCube/NSF</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The new breakthrough detection required a rather strange “telescope” that is buried several kilometres deep in the Antarctic ice cap, under the South Pole. The <a href="https://icecube.wisc.edu/">IceCube Neutrino Observatory</a> uses a gigatonne of the ultra-transparent ice under huge pressures to detect a form of energy called Cherenkov radiation. </p>
<p>This faint radiation is emitted by charged particles, which, in ice, can travel faster than light (but not in a vacuum). The particles are created by incoming neutrinos, which come from cosmic ray collisions in the galaxy, hitting the atoms in the ice.</p>
<p>Cosmic rays are mainly proton particles (these make up the atomic nucleus along with neutrons), together with a few heavy nuclei and electrons. About a century ago, these were discovered to be raining down on the Earth uniformly from all directions. We do not yet definitively know all their sources, as their travel directions are scrambled by magnetic fields that exist in the space between stars.</p>
<h2>Deep in the ice</h2>
<p>Neutrinos can act as unique tracers of cosmic ray interactions deep in the Milky Way. However, the ghostly particles are also generated when cosmic rays hit the Earth’s atmosphere. So the researchers using the IceCube data needed a way to distinguish between the neutrinos of “astrophysical” origin – those originating from extraterrestrial sources – and those created from cosmic ray collisions within our atmosphere.</p>
<p>The researchers focused on a type of neutrino interaction in the ice called a cascade. These result in roughly spherical showers of light and give the researchers a better level of sensitivity to the astrophysical neutrinos from the Milky Way. This is because a cascade provides a better measurement of a neutrino’s energy than other types of interactions, even though they are harder to reconstruct.</p>
<figure class="align-center ">
<img alt="IceCube Observatory" src="https://images.theconversation.com/files/535014/original/file-20230630-25-7iub59.jpeg?ixlib=rb-1.1.0&rect=0%2C6%2C4319%2C2892&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/535014/original/file-20230630-25-7iub59.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/535014/original/file-20230630-25-7iub59.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/535014/original/file-20230630-25-7iub59.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/535014/original/file-20230630-25-7iub59.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/535014/original/file-20230630-25-7iub59.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/535014/original/file-20230630-25-7iub59.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The IceCube Observatory is located at the South Pole.</span>
<span class="attribution"><a class="source" href="https://icecube.wisc.edu/gallery/nsf-renews-icecube-maintenance-and-operations-contract-2/#modulagallery-7041-1987">Erik Beiser, IceCube/NSF</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Analysis of ten years of IceCube data using sophisticated machine learning techniques yielded nearly 60,000 neutrino events with an energy above 500 gigaelectronvolts (GeV). Of these, only about 7% were of astrophysical origin, with the rest being due to the “background” source of neutrinos that are generated in the Earth’s atmosphere. </p>
<p>The hypothesis that all the neutrino events could be due to cosmic rays hitting the Earth’s atmosphere was definitively rejected at a level of statistical significance known as 4.5 sigma. Put another way, our result has only about a 1 in 150,000 chance of being a fluke. </p>
<p>This falls a little short of the conventional 5 sigma standard for claiming a discovery in particle physics. However, such emission from the Milky Way is expected on sound astrophysical grounds.</p>
<p>With the upcoming enlargement of the experiment – <a href="https://icecube.wisc.edu/science/beyond/">IceCube-Gen2</a> will be ten times bigger – we will acquire many more neutrino events and the current blurry picture will turn into a detailed view of our galaxy, one that we have never had before.</p><img src="https://counter.theconversation.com/content/208879/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Subir Sarkar received funding from the University of Oxford to support his participation in IceCube. </span></em></p>An observatory called IceCube was used to produce a view of our galaxy in particles rather than light.Subir Sarkar, Emeritus professor, University of OxfordLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2087432023-06-29T20:01:55Z2023-06-29T20:01:55ZIceCube neutrino detector in Antarctica spots first high-energy neutrinos emitted in our own Milky Way galaxy<figure><img src="https://images.theconversation.com/files/534884/original/file-20230629-25340-vu0a05.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6667%2C3750&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Scientists have detected the first neutrinos from our galaxy.</span> <span class="attribution"><span class="source">NSF/IceCube</span></span></figcaption></figure><p>The South Pole <a href="https://icecube.wisc.edu/">IceCube Neutrino Observatory</a> – the biggest and strangest telescope in the world – has detected the first neutrino emissions from within the Milky Way, an achievement that will shape how astronomers view our galaxy. </p>
<p><a href="https://theconversation.com/how-neutrinos-which-barely-exist-just-ran-off-with-another-nobel-prize-48726">Neutrinos</a> are tiny, electrically neutral particles that pass through most matter undetected. They are created in extreme environments like those surrounding massive black holes, and they <a href="https://icecube.wisc.edu/outreach/neutrinos/">travel unhindered through space and matter</a> in a straight path.</p>
<p>Because black holes and exploding stars are too far away to visit, and too extreme to reproduce in a laboratory, scientists rely on cosmic messengers – like visible light from stars – to study them. Neutrinos are another type of cosmic messenger, but they’re too small to be seen with our eyes, or even most types of telescopes. </p>
<p>That’s where <a href="https://icecube.wisc.edu/science/icecube/">IceCube comes in</a>. The observatory, based in Antarctica, is made of up of <a href="https://theconversation.com/scientist-at-work-searching-for-tiny-neutrinos-in-the-south-poles-thick-ice-49979">a billion tons of ice</a> equipped with a grid of frozen-in sensors. The sensors light up when they detect a neutrino passing through, and, based on the sensors’ arrangement, researchers can determine the energy and direction of the neutrino that created the flash.</p>
<p>From there, researchers can use the energy and direction to try to figure out <a href="https://theconversation.com/the-icecube-observatory-detects-neutrino-and-discovers-a-blazar-as-its-source-99720">where in the universe</a> the neutrino came from. </p>
<p>As the interim director of the <a href="https://wipac.wisc.edu/">Wisconsin IceCube Particle Astrophysics Center</a>, I ensure we have the people and resources needed to <a href="https://icecube.wisc.edu/about-us/overview/">help researchers succeed in using the IceCube observatory</a>.</p>
<h2>Detecting neutrinos using ice</h2>
<p>Identifying the flashes of light from neutrino interactions on IceCube’s sensors can be a challenge. IceCube <a href="https://icecube.wisc.edu/about-us/facts/">records about 2,600 events each second</a>, though most of these events come from high-energy particles called <a href="https://home.cern/science/physics/cosmic-rays-particles-outer-space">cosmic rays</a>, which also produce a steady rain of neutrinos upon hitting the Earth’s atmosphere. <a href="https://icecube.wisc.edu/science/research/">Only a few hundred</a> of the hundred thousand neutrinos seen each year are from galactic or extragalactic sources rather than cosmic rays.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/2DDQYHIbL3Q?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">A neutrino interacts with ice in the IceCube detector, producing light recorded by IceCube sensors and indicating its direction and energy. IceCube.</span></figcaption>
</figure>
<p>Finding the neutrinos from outer space, rather than those from cosmic rays, is like trying to see a faint feature in a portrait covered by many layers of paint – you have to be careful not to remove what you’re trying to uncover.</p>
<p>Surprisingly, the first two neutrino sources that IceCube researchers previously identified came from outside the Milky Way – <a href="https://theconversation.com/the-icecube-observatory-detects-neutrino-and-discovers-a-blazar-as-its-source-99720">one of which</a> was a very bright galactic object called a blazar. These neutrinos were quite distant, but higher-energy than any sources from within the Milky Way. </p>
<p>Finding fainter Milky Way neutrinos required some clever work by IceCube collaborators at Drexel University and Dortmund University. Their work on IceCube’s detection of the first Milky Way neutrinos was <a href="https://doi.org/10.1126/science.adc9818">published in Science on June 29, 2023</a>.</p>
<p>Scientists can use a few tricks to filter neutrinos from outer space from cosmic ray neutrinos and other cosmic ray noise. We can <a href="https://doi.org/10.1126/science.1242856">sort by energy</a>, with the higher-energy neutrinos being more likely to be from outer space. Researchers can also look for <a href="https://doi.org/10.1126/science.abg3395">clusters of neutrinos</a>, because neutrinos from outside our galaxy tend to clump together in one location. Lastly, researchers can look for neutrinos <a href="https://doi.org/10.1126/science.aat1378">from transient, astrophysical events</a> like <a href="https://doi.org/10.1126/science.aat2890">black holes</a> that have already been detected by other telescopes.</p>
<p>In 2013, IceCube published the <a href="https://doi.org/10.1126/science.1242856">first evidence of astrophysical neutrinos</a> identified based on their energy. These were isolated single neutrinos – so researchers couldn’t tell exactly where they were coming from.</p>
<h2>Searching for a neutrino’s source</h2>
<p>Even though scientists figured out that these most recently discovered neutrinos came from within our own galaxy, they don’t have a clear enough map of the Milky Way to identify the individual location where the newly uncovered neutrinos originated. Improving the analysis to determine the specific location of neutrino emission is the next step. </p>
<p>There are a few ways to improve the hunt for the sources. First, the longer scientists look and the more data they collect, the more likely they are to pinpoint a neutrino’s source – but to improve by a factor of 10 takes 100 times more data. So being clever has a better return than being patient. </p>
<p>Here are some ways to be more clever. First, researchers can <a href="https://doi.org/10.1088/1748-0221/17/11/P11003">improve the event selection</a> by choosing which cosmic events to zero in on, so that more potential neutrino candidates are in the sample. They can also <a href="https://icecube.wisc.edu/news/research/2022/11/machine-learning-method-improves-reconstruction-and-classification-of-low-energy-icecube-events/">better reconstruct the neutrinos’ path</a> – this is like revisiting a museum with new glasses to see with more clarity. Lastly, they can try to find a way to reduce the background, sort of like looking for a region where the portrait is covered by fewer layers of paint. </p>
<p>It took using all these tricks to <a href="https://doi.org/10.1126/science.adc9818">see faint Milky Way neutrinos</a>. Our team found ways to improve the sample size, and we used machine learning to improve the event reconstruction. This reduced the background enough to trace our neutrinos back to the Milky Way.</p>
<p>For most forms of cosmic light emission we study, light from sources within the Milky Way shine the brightest because they’re the closest. But for neutrinos, this isn’t the case – Galaxy NGC1068, tens of millions of light-years away, <a href="https://doi.org/10.1126/science.adc9818">emits more high-energy neutrinos</a> than the Milky Way. This tells us not all galaxies have the same ability to produce high-energy particles, but also that we need to to find and study more galaxies that emit neutrinos to understand the Milky Way’s cosmic quirks.</p>
<p>IceCube is planning a high-energy upgrade that would make the detector array <a href="https://icecube.wisc.edu/science/beyond/">about eight times larger</a>. Once the upgrade finishes in the 2030s, scientists will be able to continue their search for neutrinos with improved technology.</p><img src="https://counter.theconversation.com/content/208743/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jim Madsen works for the University of Wisconsin-Madison where is the interim director of the Wisconsin IceCube Particle Astrophysics Center (WIPAC). He receives funding from National Science Foundation to support IceCube. </span></em></p>New data from the IceCube collaboration shows neutrino emissions from within our Milky Way galaxy – but figuring out where exactly these ghost particles come from is harder than it seems.Jim Madsen, Executive Director, Wisconsin IceCube Particle Astrophysics Center, University of Wisconsin-MadisonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2086222023-06-29T20:01:42Z2023-06-29T20:01:42ZA neutrino portrait of our galaxy reveals high-energy particles from within the Milky Way<figure><img src="https://images.theconversation.com/files/534726/original/file-20230629-23-u6xkg.jpg?ixlib=rb-1.1.0&rect=643%2C0%2C1211%2C850&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">IceCube Collaboration/Science Communication Lab for CRC 1491</span></span></figcaption></figure><p>Our Milky Way galaxy is an awe-inspiring feature of the night sky, viewable with the naked eye as a hazy band of stars stretching from horizon to horizon.</p>
<p>For the first time, the IceCube Neutrino Observatory in Antarctica has produced an image of the Milky Way using neutrinos – tiny, ghost-like astronomical messengers. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/534734/original/file-20230629-25-v10rmi.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A photo of the band of the Milky Way with extra shading in blue." src="https://images.theconversation.com/files/534734/original/file-20230629-25-v10rmi.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/534734/original/file-20230629-25-v10rmi.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/534734/original/file-20230629-25-v10rmi.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/534734/original/file-20230629-25-v10rmi.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/534734/original/file-20230629-25-v10rmi.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/534734/original/file-20230629-25-v10rmi.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/534734/original/file-20230629-25-v10rmi.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A portrait of the Milky Way combining visible light and neutrino emissions (in blue).</span>
<span class="attribution"><span class="source">IceCube Collaboration/US National Science Foundation (Lily Le & Shawn Johnson)/ESO (S. Brunier)</span></span>
</figcaption>
</figure>
<p>In <a href="http://dx.doi.org/10.1126/science.adc9818">research published today</a> in the journal Science, the IceCube Collaboration – an international group of more than 350 scientists – presents evidence of high-energy neutrino emission coming from the Milky Way.</p>
<p>We have not yet figured out exactly where in our galaxy these particles are coming from. But today’s result brings us closer to finding some of the galaxy’s most extreme environments.</p>
<h2>Neutrino astronomy</h2>
<p>Neutrinos offer a unique view of the cosmos as they can travel directly from places no other radiation or particles can escape from. This makes them very interesting to astronomers, because neutrinos offer a window into the extreme cosmic environments that create another kind of particle called cosmic rays.</p>
<p>Cosmic rays are high-energy particles that permeate our Universe, but their origins are difficult to pin down. Cosmic rays are electrically charged, which means their path through space is scrambled by magnetic fields, and by the time one arrives at Earth there is no way to tell where it came from. </p>
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Read more:
<a href="https://theconversation.com/spotting-astrophysical-neutrinos-is-just-the-tip-of-the-icecube-20499">Spotting astrophysical neutrinos is just the tip of the IceCube</a>
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<p>However, the environments that accelerate cosmic rays to extraordinary energies also produce neutrinos – and neutrinos have no electric charge, so they travel in nice straight lines. So if we can detect the path of neutrinos arriving at Earth, this will point back to where the neutrinos were created. </p>
<p>But detecting those neutrinos is not so easy. </p>
<h2>How to hunt neutrinos</h2>
<p>The IceCube Neutrino Observatory is not far from the South Pole. It uses more than 5,000 light sensors arrayed throughout a cubic kilometre of pristine Antarctic ice to search for signs of high-energy neutrinos from our galaxy and beyond. </p>
<p>Vast numbers of neutrinos are streaming through Earth all the time, but only a tiny fraction of them bump into anything on their way through.</p>
<p>Each neutrino interaction makes a tiny flash of light – and those tiny flashes are what the IceCube sensors look out for. The direction and energy of the neutrino can be determined from the amount and pattern of light detected.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/534733/original/file-20230629-23-b8qav.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/534733/original/file-20230629-23-b8qav.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/534733/original/file-20230629-23-b8qav.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/534733/original/file-20230629-23-b8qav.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/534733/original/file-20230629-23-b8qav.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/534733/original/file-20230629-23-b8qav.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/534733/original/file-20230629-23-b8qav.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/534733/original/file-20230629-23-b8qav.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">IceCube Collaboration</span></span>
</figcaption>
</figure>
<p>IceCube has previously detected high-energy neutrinos coming from outside the Milky Way. However, it has been more challenging to isolate the lower-energy neutrinos coming from within our galaxy.</p>
<p>This is because some flashes IceCube detected can be traced to cosmic rays hitting Earth’s atmosphere, which create neutrinos and other particles called muons. To filter out these flashes, IceCube researchers have developed ways to distinguish particles created in the atmosphere and those from further afield by the shape of the light patterns they create in the ice. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/an-antarctic-neutrino-telescope-has-detected-a-signal-from-the-heart-of-a-nearby-active-galaxy-193845">An Antarctic neutrino telescope has detected a signal from the heart of a nearby active galaxy</a>
</strong>
</em>
</p>
<hr>
<p>Filtering out the unwanted detections has made IceCube more sensitive to astrophysical neutrinos. The final breakthrough that allowed the creation of a neutrino image of the Milky Way came from machine-learning methods that improve the identification of cascades of light produced by neutrinos, as well as the determination of the neutrino’s direction and energy.</p>
<h2>Closing in on cosmic rays</h2>
<p>The new neutrino lens on our galaxy will help reveal where the most powerful accelerators of galactic cosmic rays are located. We hope to learn how energetic these particles can get, and the inner workings of these high-energy galactic engines.</p>
<p>However, we are yet to pinpoint these accelerators within the Milky Way. The new IceCube analysis found evidence for neutrinos coming from broad regions of the galaxy, but was not able to discern individual sources.</p>
<p>Our team, at the University of Canterbury in New Zealand and the University of Adelaide in Australia, has a plan to realise that next step.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/534735/original/file-20230629-17-4f6jrd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/534735/original/file-20230629-17-4f6jrd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/534735/original/file-20230629-17-4f6jrd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=342&fit=crop&dpr=1 600w, https://images.theconversation.com/files/534735/original/file-20230629-17-4f6jrd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=342&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/534735/original/file-20230629-17-4f6jrd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=342&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/534735/original/file-20230629-17-4f6jrd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=430&fit=crop&dpr=1 754w, https://images.theconversation.com/files/534735/original/file-20230629-17-4f6jrd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=430&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/534735/original/file-20230629-17-4f6jrd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=430&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Five views of the Milky Way: the top two bands show visible light and gamma rays, while the lower three show expected and real neutrino results, plus a measure of the significance of neutrino events detected by IceCube.</span>
<span class="attribution"><span class="source">IceCube Collaboration</span></span>
</figcaption>
</figure>
<p>We are making models to predict the neutrino signal close to likely particle accelerators so we can target our searches for neutrinos. </p>
<p>Undergraduate student Rhia Hewett and PhD student Ryan Burley are examining pairs of accelerator candidates and molecular dust clouds. They plan to estimate the flux of neutrinos produced by cosmic rays interacting in the clouds, after the neutrinos travel from the accelerators. </p>
<p>They will use their results to enable a focused search of IceCube data for the sources of neutrino emissions. We believe this will provide the key to using IceCube to unlock the secrets of the most energetic processes in the Milky Way.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/534731/original/file-20230629-22-fmkvpi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/534731/original/file-20230629-22-fmkvpi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/534731/original/file-20230629-22-fmkvpi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=2067&fit=crop&dpr=1 600w, https://images.theconversation.com/files/534731/original/file-20230629-22-fmkvpi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=2067&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/534731/original/file-20230629-22-fmkvpi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=2067&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/534731/original/file-20230629-22-fmkvpi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=2597&fit=crop&dpr=1 754w, https://images.theconversation.com/files/534731/original/file-20230629-22-fmkvpi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=2597&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/534731/original/file-20230629-22-fmkvpi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=2597&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A timeline of neutrino astronomy.</span>
<span class="attribution"><span class="source">IceCube Collaboration</span></span>
</figcaption>
</figure><img src="https://counter.theconversation.com/content/208622/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jenni Adams has received funding from the Marsden Fund Council from New Zealand Government funding, managed by the Royal Society Te Apārangi. </span></em></p>Neutrinos are some of nature’s most elusive particles, but new research has used them to create an image of our own galaxy.Jenni Adams, Professor, Physics and Astronomy, University of CanterburyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2033082023-04-18T16:12:00Z2023-04-18T16:12:00ZBuilding telescopes on the Moon could transform astronomy – and it’s becoming an achievable goal<figure><img src="https://images.theconversation.com/files/520796/original/file-20230413-117-illn0w.jpeg?ixlib=rb-1.1.0&rect=3%2C1%2C1013%2C570&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The far side of the Moon is an attractive place to carry out astronomy.</span> <span class="attribution"><a class="source" href="https://svs.gsfc.nasa.gov/11747">NASA / Ernie Wright</a></span></figcaption></figure><p>Lunar exploration is undergoing a renaissance. <a href="https://en.wikipedia.org/wiki/List_of_missions_to_the_Moon">Dozens of missions</a>, organised by multiple space agencies – and increasingly by commercial companies – are set to visit the Moon by the end of this decade. Most of these will involve small robotic spacecraft, but NASA’s ambitious <a href="https://theconversation.com/astronauts-are-returning-to-the-moon-but-they-wont-be-repeating-the-apollo-missions-202489">Artemis programme</a>, aims to return humans to the lunar surface by the middle of the decade.</p>
<p>There are various reasons for all this activity, including geopolitical posturing and the search for lunar resources, such as <a href="https://www.technologyreview.com/2020/05/19/1001857/how-moon-lunar-mining-water-ice-rocket-fuel/">water-ice at the lunar poles</a>, which can be extracted and turned into hydrogen and oxygen propellant for rockets. However, science is also sure to be a major beneficiary. </p>
<p>The Moon <a href="https://esamultimedia.esa.int/docs/HRE/03_PhysicalSciences_Planetary_Science.pdf">still has much to tell us</a> about the origin and evolution of the solar system. It also has scientific value as a platform for observational astronomy. </p>
<p>The potential role for astronomy of Earth’s natural satellite was discussed at a <a href="https://royalsociety.org/science-events-and-lectures/2023/02/astronomy-moon/">Royal Society meeting</a> earlier this year. The meeting itself had, in part, been sparked by the enhanced access to the lunar surface now in prospect.</p>
<h2>Far side benefits</h2>
<p>Several types of astronomy would benefit. The most obvious is radio astronomy, which can be conducted from the side of the Moon that always faces away from Earth – the far side. </p>
<p>The lunar far side is permanently shielded from the radio signals generated by humans on Earth. During the lunar night, it is also protected from the Sun. These characteristics make it probably <a href="https://royalsocietypublishing.org/toc/rsta/2021/379/2188?volume=379&vol=379&issue=2188&publicationCode=rsta">the most “radio-quiet” location in the whole solar system</a> as no other planet or moon has a side that permanently faces away from the Earth. It is therefore ideally suited for radio astronomy.</p>
<p>Radio waves are a form of electromagnetic energy – as are, for example, infrared, ultraviolet and visible-light waves. They are defined by having different wavelengths in the electromagnetic spectrum. </p>
<p>Radio waves with wavelengths longer than about 15m are blocked by Earth’s <a href="https://en.wikipedia.org/wiki/Ionosphere">ionoshere</a>. But radio waves at these wavelengths reach the Moon’s surface unimpeded. For astronomy, this is the last unexplored region of the electromagnetic spectrum, and it is best studied from the lunar far side.</p>
<p>Observations of the cosmos at these wavelengths come under the umbrella of “low frequency radio astronomy”. These wavelengths are uniquely able to probe the structure of the early universe, especially the cosmic “<a href="https://en.wikipedia.org/wiki/Chronology_of_the_universe#Dark_Ages">dark ages</a>” – an era before the first galaxies formed. </p>
<p>At that time, most of the matter in the universe, excluding the mysterious <a href="https://en.wikipedia.org/wiki/Dark_matter">dark matter</a>, was in the form of neutral hydrogen atoms. These emit and absorb radiation with a characteristic wavelength of 21cm. Radio astronomers have been using this property to study hydrogen clouds in our own galaxy – the Milky Way – since the 1950s. </p>
<p>Because the universe is constantly expanding, the 21cm signal generated by hydrogen in the early universe has been shifted to much longer wavelengths. As a result, hydrogen from the cosmic “dark ages” will appear to us with wavelengths greater than 10m. The lunar far side may be the only place where we can study this. </p>
<p>The astronomer Jack Burns provided a good summary of the relevant <a href="https://royalsocietypublishing.org/doi/10.1098/rsta.2019.0564">science background</a> at the recent Royal Society meeting, calling the far side of the moon a “pristine, quiet platform to conduct low radio frequency observations of the early Universe’s Dark Ages, as well as space weather and magnetospheres associated with habitable exoplanets”.</p>
<h2>Signals from other stars</h2>
<p>As Burns says, another potential application of far side radio astronomy is trying to detect radio waves from charged particles trapped by magnetic fields – <a href="https://en.wikipedia.org/wiki/Magnetosphere">magnetospheres</a> – of planets orbiting other stars. </p>
<p>This would help to assess how capable these exoplanets are of hosting life. Radio waves from exoplanet magnetospheres would probably have wavelengths greater than 100m, so they would require a radio-quiet environment in space. Again, the far side of the Moon will be the best location.</p>
<p>A similar argument can be made for <a href="https://www.smithsonianmag.com/science-nature/why-astronomers-want-build-seti-observatory-moon-180975966/">attempts to detect signals from intelligent aliens</a>. And, by opening up an unexplored part of the radio spectrum, there is also the possibility of making serendipitous discoveries of new phenomena.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/520108/original/file-20230410-5761-65x14.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/520108/original/file-20230410-5761-65x14.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=412&fit=crop&dpr=1 600w, https://images.theconversation.com/files/520108/original/file-20230410-5761-65x14.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=412&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/520108/original/file-20230410-5761-65x14.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=412&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/520108/original/file-20230410-5761-65x14.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=518&fit=crop&dpr=1 754w, https://images.theconversation.com/files/520108/original/file-20230410-5761-65x14.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=518&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/520108/original/file-20230410-5761-65x14.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=518&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Artist’s conception of the LuSEE-Night radio astronomy experiment on the Moon (credit: Nasa/Tricia Talbert)</span>
</figcaption>
</figure>
<p>We should get an indication of the potential of these observations when NASA’s <a href="https://physics.berkeley.edu/news/lusee-night-will-attempt-first-its-kind-measurements-dark-ages-universe">LuSEE-Night mission</a> lands on the lunar far side in 2025 or 2026. </p>
<h2>Crater depths</h2>
<p>The Moon also offers opportunities for other types of astronomy as well. Astronomers have lots of experience with optical and infrared telescopes operating in free space, such as the <a href="https://www.nasa.gov/mission_pages/hubble/main/index.html">Hubble telescope</a> and <a href="https://webb.nasa.gov">JWST</a>. However, the stability of the lunar surface may confer advantages for these types of instrument.</p>
<p>Moreover, there are <a href="https://en.wikipedia.org/wiki/Permanently_shadowed_crater">craters</a> at the lunar poles that receive no sunlight. Telescopes that observe the universe at infrared wavelengths are very sensitive to heat and therefore have to operate at low temperatures. JWST, for example, needs a huge sunshield to protect it from the sun’s rays. On the Moon, a natural crater rim could provide this shielding for free. </p>
<figure class="align-center ">
<img alt="A permanently shadowed lunar crater" src="https://images.theconversation.com/files/520990/original/file-20230414-20-s56de3.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/520990/original/file-20230414-20-s56de3.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/520990/original/file-20230414-20-s56de3.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/520990/original/file-20230414-20-s56de3.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/520990/original/file-20230414-20-s56de3.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/520990/original/file-20230414-20-s56de3.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/520990/original/file-20230414-20-s56de3.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Permanently shadowed craters at the lunar poles could eventually host infrared telescopes.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/feature/goddard/2019/inside-dark-polar-moon-craters-water-not-as-invincible-as-expected-scientists-argue">LROC / ASU / NASA</a></span>
</figcaption>
</figure>
<p>The Moon’s low gravity may also enable the <a href="https://royalsocietypublishing.org/doi/10.1098/rsta.2019.0570">construction of much larger telescopes</a> than is feasible for free-flying satellites. These considerations have led the astronomer Jean-Pierre Maillard to suggest that the Moon may be the <a href="https://royalsocietypublishing.org/doi/10.1098/rsta.2020.0212">future of infrared astronomy</a>. </p>
<p>The cold, stable environment of permanently shadowed craters may also have advantages for the next generation of instruments to detect <a href="https://arxiv.org/abs/2205.07255">gravitational waves</a> – “ripples” in space-time caused by processes such as exploding stars and colliding black holes. </p>
<p>Moreover, for billions of years the Moon has been bombarded by charged particles from the sun – solar wind – and galactic cosmic rays. The lunar surface may contain a <a href="https://royalsocietypublishing.org/doi/10.1098/rsta.2019.0562">rich record of these processes</a>. Studying them could yield insights into the evolution of both the Sun and the Milky Way. </p>
<p>For all these reasons, astronomy stands to benefit from the current renaissance in lunar exploration. In particular, astronomy is likely to benefit from the infrastructure built up on the Moon as lunar exploration proceeds. This will include both transportation infrastructure – rockets, landers and other vehicles – to access the surface, as well as humans and robots on-site to construct and maintain astronomical instruments.</p>
<p>But there is also a tension here: human activities on the lunar far side may create unwanted radio interference, and plans to extract water-ice from shadowed craters might make it difficult for those same craters to be used for astronomy. As my colleagues and I recently <a href="https://arxiv.org/abs/2212.01363">argued</a>, we will need to ensure that lunar locations that are uniquely valuable for astronomy are protected in this new age of lunar exploration.</p><img src="https://counter.theconversation.com/content/203308/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ian Crawford is a member of the UK Space Agency's Space Exploration Advisory Committee (SEAC) and has advised the European Space Agency on lunar exploration policy. He is chair of COSPAR sub-commission B3 (Moon), and a member of the Moon Village Association which aims to foster international cooperation in lunar exploration. He was a co-organiser of the recent Royal Society meeting "Astronomy from the Moon."</span></em></p>The current race to the Moon is opening up opportunities for lunar astronomy.Ian Crawford, Professor of Planetary Science and Astrobiology, Birkbeck, University of London, Honorary Associate Professor, UCLLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1979052023-01-16T22:13:08Z2023-01-16T22:13:08ZAstronomers reveal the most detailed radio image yet of the Milky Way’s galactic plane<figure><img src="https://images.theconversation.com/files/504592/original/file-20230116-19027-nxt92l.jpg?ixlib=rb-1.1.0&rect=264%2C0%2C1930%2C1103&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Combined images from the ASKAP and Parkes radio telescopes.</span> <span class="attribution"><span class="source">R. Kothes (NRC) and the PEGASUS team</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Two major astronomy research programs, called EMU and PEGASUS, have joined forces to resolve one of the mysteries of our Milky Way: where are all the supernova remnants? </p>
<p>A <a href="https://theconversation.com/a-new-australian-supercomputer-has-already-delivered-a-stunning-supernova-remnant-pic-188375">supernova remnant</a> is an expanding cloud of gas and dust marking the last phase in the life of a star, after it has exploded as a supernova. But the number of supernova remnants we have detected so far with radio telescopes is too low. Models predict five times as many, so where are the missing ones? </p>
<p>We have combined observations from two of Australia’s world-leading radio telescopes, the <a href="https://www.csiro.au/en/about/facilities-collections/ATNF/ASKAP-radio-telescope">ASKAP radio telescope</a> and the <a href="https://www.csiro.au/en/about/facilities-collections/atnf/parkes-radio-telescope">Parkes radio telescope, Murriyang</a>, to answer this question.</p>
<h2>The gas between the stars</h2>
<figure>
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<figcaption>Comparison between the ASKAP/EMU image and the combined ASKAP/EMU plus Parkes/PEGASUS image. <br>Images: R. Kothes (NRC) and E. Carretti (INAF).</figcaption>
</figure>
<p>The new image reveals thin tendrils and clumpy clouds associated with hydrogen gas filling the space between the stars. We can see sites where new stars are forming, as well as supernova remnants.</p>
<p>In just this small patch, only about 1% of the whole Milky Way, we have discovered more than 20 new possible supernova remnants where only seven were previously known. </p>
<p>These discoveries were led by PhD student Brianna Ball from Canada’s University of Alberta, working with her supervisor, Roland Kothes of the National Research Council of Canada, who prepared the image. These new discoveries suggest we are close to accounting for the missing remnants.</p>
<p>So why can we see them now when we couldn’t before?</p>
<figure class="align-center ">
<img alt="The ASKAP radio telescope, showing radio dishes pointed at a blue sky with the sun in the background." src="https://images.theconversation.com/files/504590/original/file-20230116-18-23rt6s.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/504590/original/file-20230116-18-23rt6s.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/504590/original/file-20230116-18-23rt6s.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/504590/original/file-20230116-18-23rt6s.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/504590/original/file-20230116-18-23rt6s.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=565&fit=crop&dpr=1 754w, https://images.theconversation.com/files/504590/original/file-20230116-18-23rt6s.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=565&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/504590/original/file-20230116-18-23rt6s.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=565&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The ASKAP radio telescope at Inyarrimanha Ilgari Bundara, the CSIRO Murchison Radio-astronomy Observatory in Western Australia.</span>
<span class="attribution"><span class="source">CSIRO</span></span>
</figcaption>
</figure>
<h2>The power of joining forces</h2>
<p>I lead the <a href="http://www.emu-survey.org/">Evolutionary Map of the Universe</a> or EMU program, an ambitious project with ASKAP to make the best radio atlas of the Southern Hemisphere.</p>
<p>EMU will measure about 40 million new distant galaxies and supermassive black holes, to help us understand how galaxies have changed over the history of the universe.</p>
<p>Early EMU data have already led to the discovery of <a href="https://theconversation.com/odd-radio-circles-that-baffled-astronomers-are-likely-explosions-from-distant-galaxies-178290">odd radio circles (or “ORCs”)</a>, and revealed <a href="https://theconversation.com/dancing-ghosts-a-new-deeper-scan-of-the-sky-throws-up-surprises-for-astronomers-165239">rare oddities like the “Dancing Ghosts”</a>.</p>
<p>For any telescope, the resolution of its images depends on the size of its aperture. Interferometers like ASKAP simulate the aperture of a much larger telescope. With 36 relatively small dishes (each 12m in diameter) but a 6km distance connecting the farthest of these, ASKAP mimics a single telescope with a 6km wide dish.</p>
<p>That gives ASKAP a good resolution, but comes at the expense of missing radio emission on the largest scales. In the comparison above, the ASKAP image alone appears too skeletal.</p>
<figure class="align-center ">
<img alt="The Parkes radio telescope, Murriyang, showing the 64 telescope dish." src="https://images.theconversation.com/files/504591/original/file-20230116-16-v7ugns.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/504591/original/file-20230116-16-v7ugns.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/504591/original/file-20230116-16-v7ugns.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/504591/original/file-20230116-16-v7ugns.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/504591/original/file-20230116-16-v7ugns.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=423&fit=crop&dpr=1 754w, https://images.theconversation.com/files/504591/original/file-20230116-16-v7ugns.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=423&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/504591/original/file-20230116-16-v7ugns.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=423&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Parkes radio telescope, Murriyang.</span>
<span class="attribution"><span class="source">CSIRO</span></span>
</figcaption>
</figure>
<p>To recover that missing information, we turned to a companion project called PEGASUS, led by Ettore Carretti of Italy’s National Institute of Astrophysics.</p>
<p>PEGASUS uses the 64m diameter Parkes/Murriyang telescope – one of the largest single-dish radio telescopes in the world – to map the sky.</p>
<p>Even with such a large dish, Parkes has rather limited resolution. By combining the information from both Parkes and ASKAP, each fills in the gaps of the other to give us the best fidelity image of this region of our Milky Way galaxy. This combination reveals the radio emission on all scales to help uncover the missing supernova remnants.</p>
<p>Linking the datasets from EMU and PEGASUS will allow us to reveal more hidden gems. In the next few years we will have an unprecedented view of almost the entire Milky Way, about a hundred times larger than this initial image, but with the same level of detail and sensitivity.</p>
<p>We estimate there may be up to 1,500 or more new supernova remnants yet to discover. Solving the puzzle of these missing remnants will open new windows into the history of our Milky Way.</p>
<hr>
<p><em>ASKAP and Parkes are owned and operated by CSIRO, Australia’s national science agency, as part of the Australia Telescope National Facility. CSIRO acknowledge the Wajarri Yamaji people as the Traditional Owners and native title holders of Inyarrimanha Ilgari Bundara, the CSIRO Murchison Radio-astronomy Observatory, where ASKAP is located, and the Wiradjuri people as the traditional owners of the Parkes Observatory.</em></p><img src="https://counter.theconversation.com/content/197905/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew Hopkins does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Our galaxy should be full of traces of dead stars. Until now, we have found surprisingly few of these supernova remnants, but a new telescope collaboration is changing that.Andrew Hopkins, Professor of Astronomy, Macquarie UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1934202022-11-17T17:51:16Z2022-11-17T17:51:16ZCurious Kids: how many galaxies are there in the universe?<figure><img src="https://images.theconversation.com/files/494458/original/file-20221109-11121-yn67m.jpg?ixlib=rb-1.1.0&rect=0%2C13%2C4374%2C2898&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/boys-girls-telescopic-milky-way-galaxy-525251419">Sunti/Shutterstock</a></span></figcaption></figure><p><strong>How many galaxies are there beyond the Milky Way? – Rosella, aged 15, Hong Kong</strong></p>
<p>A <a href="https://www.nationalgeographic.com/science/article/galaxies">galaxy</a> is a massive collection of gas, dust and billions of stars all bound together by the force of gravity. Galaxies are also huge, measuring <a href="https://imagine.gsfc.nasa.gov/features/cosmic/milkyway_info.html">billions of billions of kilometres across</a>. </p>
<p>To properly understand what a galaxy is, we should start by looking at our own Milky Way galaxy.</p>
<p>Our Sun is just one star out of <a href="https://www.space.com/25959-how-many-stars-are-in-the-milky-way.html">billions of other stars</a> contained within a galaxy called the Milky Way. In the same way that the Earth orbits the Sun, the Sun also orbits the Milky Way’s centre.</p>
<p>When we look up at the night sky, the stars we can see with our eyes are all part of the Milky Way. If you’ve been outside on a really clear, dark night, you may have noticed a thin fuzzy band of stars and light stretching across the sky. This is our Milky Way galaxy viewed from the inside out. We see a thin line because our galaxy is shaped like a thin disk, and we’re looking at the edge of the disk. </p>
<hr>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><em><a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a> is a series by <a href="https://theconversation.com/uk">The Conversation</a> that gives children the chance to have their questions about the world answered by experts. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskids@theconversation.com">curiouskids@theconversation.com</a> and make sure you include the asker’s first name, age and town or city. We won’t be able to answer every question, but we’ll do our very best.</em></p>
<hr>
<p>If we look towards the centre of this disk, we see a brighter region called the galactic core. Stars in the core are grouped much closer together, and form a shape that looks like a ball that peeks out from the top and bottom of the disk. </p>
<p>By <a href="https://solarsystem.nasa.gov/resources/285/the-milky-way-galaxy/#:%7E:text=Our%20Sun%20lies%20near%20a,the%20Sagittarius%20and%20Perseus%20arms.">mapping the positions and motions of the stars in the Milky Way</a>, we can start to build a picture of what our galaxy might look like if we could look down on the disk from above. The overall shape would be a circle. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/493141/original/file-20221102-12-pgaf8v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An artist's impression of the Milky Way galaxy, as seen from the outside. The galaxy has a bright central core and spiral arms that wind out from its centre. The overall shape is similar to a pinwheel" src="https://images.theconversation.com/files/493141/original/file-20221102-12-pgaf8v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/493141/original/file-20221102-12-pgaf8v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/493141/original/file-20221102-12-pgaf8v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/493141/original/file-20221102-12-pgaf8v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/493141/original/file-20221102-12-pgaf8v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/493141/original/file-20221102-12-pgaf8v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/493141/original/file-20221102-12-pgaf8v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">An artist’s impression of the Milky Way galaxy, as it would appear if we could see it from the outside.</span>
<span class="attribution"><a class="source" href="https://www.eso.org/public/images/eso1339g/">NASA/JPL-Caltech/ESO/R. Hurt</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>We would see the bright core, which would look reddish-yellow, <a href="https://www.skyatnightmagazine.com/space-science/star-colours/">as the stars here are cooler</a>. Winding out from that core would be a number of spiral arms, bluish in colour because they contain hotter stars. The Milky Way would look a little like a whirlpool.</p>
<h2>Beyond the Milky Way</h2>
<p>Astronomers are confident that our Milky Way has spiral arms because we see lots of other galaxies like it when we look out into the universe. Most other galaxies that are thin disks similar to our Milky Way also have winding spiral arms. We call these <a href="https://www.space.com/22382-spiral-galaxy.html">spiral galaxies</a>. </p>
<p>Not every galaxy looks this way, though. Some of the other galaxies we see in the universe look like smooth, fuzzy ovals of light, something between the shape of a basketball and a rugby ball. We call these <a href="https://www.space.com/22395-elliptical-galaxies.html">elliptical galaxies</a>, and they are mostly made up of cooler, redder stars. There are also galaxies that don’t have any particular shape at all. These are called <a href="https://spaceplace.nasa.gov/galactic-explorer/en/#:%7E:text=Irregular%20galaxies%20are%20among%20the,nearby%20galaxies%20are%20irregular%20galaxies.">irregular galaxies</a>.</p>
<p>Working out how many galaxies there are in the universe is actually pretty difficult. Many galaxies are too faint or small for us to observe easily, even with the most powerful telescopes. Despite this, astronomers came up with a clever way of working this out. Astronomers pointed the <a href="https://www.nasa.gov/mission_pages/hubble/main/index.html">Hubble space telescope</a> at a <a href="https://esahubble.org/images/heic0611b/">tiny patch of the sky</a> for 11.3 days and collected the light from galaxies that are both nearby and very distant.</p>
<figure class="align-center ">
<img alt="An image of the night sky, containing almost 10,000 galaxies. The galaxies are a variety of shapes and colours" src="https://images.theconversation.com/files/494475/original/file-20221109-2908-3poafg.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/494475/original/file-20221109-2908-3poafg.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/494475/original/file-20221109-2908-3poafg.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/494475/original/file-20221109-2908-3poafg.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/494475/original/file-20221109-2908-3poafg.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/494475/original/file-20221109-2908-3poafg.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/494475/original/file-20221109-2908-3poafg.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Hubble Ultra Deep Field image. This image of a tiny patch of sky taken by the Hubble Space Telescope shows almost 10,000 individual galaxies.</span>
<span class="attribution"><a class="source" href="https://esahubble.org/images/heic0611b/">NASA, ESA, and S. Beckwith (STScI) and the HUDF Team</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>This tiny patch of sky was full of galaxies, almost 10,000, of all different sizes and shapes. By multiplying this number by the number of times this tiny patch of sky would fit into the entire sky, astronomers came up with an estimate of <a href="https://www.space.com/25303-how-many-galaxies-are-in-the-universe.html">between about 100 and 200 billion galaxies</a>. This number will almost definitely change, though, as we learn more about our universe in the future.</p><img src="https://counter.theconversation.com/content/193420/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nicolas Bonne receives funding from the Science and Technology Facilities Council. </span></em></p>Many galaxies are too faint or small for us to observe easily – but science can help us work it out.Nicolas Bonne, Public Engagement and Outreach Fellow/Tactile Universe Project Lead, University of PortsmouthLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1831392022-05-17T15:29:21Z2022-05-17T15:29:21ZAfrican scientists and technology could drive future black hole discoveries<figure><img src="https://images.theconversation.com/files/463262/original/file-20220516-11-yif57t.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Milky Way above a single MeerKAT antenna in the Northern Cape Province of South Africa. Inset: EHT image of the Milky Way black hole. </span> <span class="attribution"><span class="source">SARAO, EHT</span></span></figcaption></figure><p>Astronomers <a href="https://eventhorizontelescope.org/blog/astronomers-reveal-first-image-black-hole-heart-our-galaxy">have revealed</a> the first image of the black hole at the centre of our galaxy, the Milky Way. The image was produced by the Event Horizon Telescope (EHT) Collaboration, an international team made up of over 300 scientists on five continents – including Africa.</p>
<p>Black holes were predicted by Albert Einstein’s <a href="https://www.space.com/17661-theory-general-relativity.html">General Theory of Relativity</a> over a century ago. They are regions of space so dense that nothing, including light, can escape. Their boundary is known as the event horizon, which marks the point of no return. That’s just one of the reasons these objects are hidden from our eyes. The other is that they are exceedingly small, when placed in their cosmic context. If our Milky Way galaxy were the size of a soccer field, its black hole event horizon would be a million times smaller than a pin prick at centrefield.</p>
<p>How, then, can one photograph them? Our team did so by capturing light from the hot swirling gas in the immediate vicinity of the black hole. This light, with a wavelength of 1 millimetre, is recorded by a global network of antennas that form a single, Earth-sized virtual telescope. </p>
<p>The light looks rather like a ring, a characteristic signature that is the direct consequence of two key processes. First, the black hole is so dense that it bends the path of light near it. Second, it captures light that strays too close to the event horizon. The combined effect produces a so-called black hole shadow - a brightened ring surrounding a distinct deficit of light centred on the black hole. In the case of our Milky Way black hole, this ring has the apparent size of a doughnut on the moon, requiring an extraordinary engineering effort to bring it into focus. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-we-captured-first-image-of-the-supermassive-black-hole-at-centre-of-the-milky-way-183010">How we captured first image of the supermassive black hole at centre of the Milky Way</a>
</strong>
</em>
</p>
<hr>
<p>The unveiling of an image of our black hole, <a href="https://theconversation.com/say-hello-to-sagittarius-a-the-black-hole-at-the-center-of-the-milky-way-galaxy-183008">Sagittarius A*</a>, is not just a massive moment for science. It could also be an important catalyst for diversifying African astrophysics research using existing strengths. We were the only two of more than 300 EHT team members based on the African continent. The continent doesn’t host any EHT telescopes – we were brought on board because of expertise we’ve developed in preparation for the world’s largest radio telescope, the <a href="https://www.skatelescope.org/">Square Kilometre Array</a> (SKA), to be co-hosted by South Africa and Australia.</p>
<h2>Why the image is important</h2>
<p>This is not the first time a black hole image has captured people’s attention. We were also members of the team that captured the <a href="https://www.nationalgeographic.com/science/article/first-picture-black-hole-revealed-m87-event-horizon-telescope-astrophysics">first ever image of a black hole in 2019</a> (this one is at the centre of a different galaxy, Messier 87, which is 55 million light years away). <a href="https://www.capjournal.org/issues/26/26_11.pdf">It has been estimated</a> that more than 4.5 billion people saw that image. Sagittarius A* has also dominated headlines and captured people’s imaginations.</p>
<p>But there’s more to this result than just an incredible image. A plethora of rich scientific results has been described in <a href="https://iopscience.iop.org/journal/2041-8205/page/Focus_on_First_Sgr_A_Results">ten publications</a> by the team. Here are three of our primary highlights.</p>
<p>First, the image is a remarkable validation of Einstein’s General Theory of Relativity. The EHT has now imaged two black holes with masses that differ by a factor of over 1000. Despite the dramatic difference in mass, the measured size and shape are consistent with theoretical predictions.</p>
<p>Second, we have now imaged black holes with very different environments. A wealth of prior research over the past two or three decades shows strong empirical evidence that galaxies and their black holes co-evolve over cosmic time, despite their completely disparate sizes. By zooming into the event horizon of black holes in giant galaxies like M87, as well as more typical galaxies like our own Milky Way, we learn more about how this seemingly implausible relationship between the black hole and its host galaxy plays out. </p>
<p>Third, the image provides us with new insights on the central black hole in our own galactic home. It is the nearest such beast to Earth, so it provides a unique laboratory to understand this interplay – not unlike scrutinising a tree in your own garden to better understand the forests on the distant horizon. </p>
<h2>Southern Africa’s geographic advantage</h2>
<p>We are proud to be part of the team that produced the first black hole images. In future, we believe South Africa, and the African continent more broadly (including <a href="https://www.ru.nl/astrophysics/radboud-radio-lab/projects/africa-millimetre-telescope-amt/">a joint Dutch-Namibian initiative</a>), could play a critical role in making the first black hole movies. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/combined-power-of-two-telescopes-is-helping-crack-the-mystery-of-eerie-rings-in-the-sky-180595">Combined power of two telescopes is helping crack the mystery of eerie rings in the sky</a>
</strong>
</em>
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<p>As has been the case with the country’s key role in paleoanthropology, there are contributions to global astronomy that can only be made from South African soil. Sagittarius A* lies in the southern sky, passing directly above South Africa. That is a major reason why this image of the Milky Way’s centre, taken by the MeerKAT (a precursor to the SKA) is the best there is. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/463268/original/file-20220516-25-mk91ce.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/463268/original/file-20220516-25-mk91ce.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/463268/original/file-20220516-25-mk91ce.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=393&fit=crop&dpr=1 600w, https://images.theconversation.com/files/463268/original/file-20220516-25-mk91ce.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=393&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/463268/original/file-20220516-25-mk91ce.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=393&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/463268/original/file-20220516-25-mk91ce.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=494&fit=crop&dpr=1 754w, https://images.theconversation.com/files/463268/original/file-20220516-25-mk91ce.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=494&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/463268/original/file-20220516-25-mk91ce.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=494&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The MeerKAT Galactic Centre image (top). Predicted snapshot imaging performance (bottom middle), based on a simulated black hole movie (bottom left), using an African-enhanced EHT array (bottom right).</span>
<span class="attribution"><span class="source">Heywood et al. (2022) / SARAO, M. Johnson (Harvard & Smithsonian)</span></span>
</figcaption>
</figure>
<p>South Africa also has well-established infrastructure at its astronomical sites, which are protected by legislation. And it has world-class engineers at the forefront of their craft. This makes for low-cost, high-performance telescopes delivered on time and to budget. </p>
<p>New technology is also on our side: a cutting-edge simultaneous multi-frequency receiver design, pioneered by our Korean colleagues, means that EHT sites no longer need to be the most pristine, high-altitude locations on Earth.</p>
<p>All the elements are in place for a dramatic increase in the number of young Africans who participate in this new era of black hole imaging and precision tests of gravity. In the coming years, we hope to be writing about findings that couldn’t have been made without technology on South African soil, as well as African scientists leading high-impact, high-visibility EHT science in synergy with our multi-wavelength astronomy and high-energy astrophysics programmes.</p><img src="https://counter.theconversation.com/content/183139/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Roger Deane receives research funding from the South African Radio Astronomy Observatory, which is a facility of the National Research Foundation (NRF), an agency of the Department of Science and Innovation (DSI) of South Africa. </span></em></p><p class="fine-print"><em><span>Iniyan Natarajan receives research funding from the South African Radio Astronomy Observatory, which is a facility of the National Research Foundation (NRF), an agency of the Department of Science and Innovation (DSI) of South Africa.</span></em></p>Sagittarius A* lies in the southern sky, passing directly above South Africa.Roger Deane, Director: Wits Centre for Astrophysics; SKA Chair in Radio Astronomy, University of the WitwatersrandIniyan Natarajan, Postdoctoral Research Fellow, Wits Centre for Astrophysics, University of the WitwatersrandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1805082022-05-02T20:43:42Z2022-05-02T20:43:42ZWe’ve used a new technique to discover the brightest radio pulsar outside our own galaxy<figure><img src="https://images.theconversation.com/files/459633/original/file-20220426-24-1yteib.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C1876%2C1235&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Artist's impression of the PSR J0523-7125 in the Large Magellanic Cloud. </span> <span class="attribution"><span class="source">Carl Knox, ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav)</span>, <span class="license">Author provided</span></span></figcaption></figure><p>When a star explodes and dies in a supernova, it takes on a new life of sorts. </p>
<p>Pulsars are the extremely rapidly rotating objects left over after massive stars have exhausted their fuel supply. They are extremely dense, with a mass similar to the Sun crammed into a region the size of Sydney. </p>
<p>Pulsars emit beams of radio waves from their poles. As those beams sweep across Earth, we can detect rapid pulses as often as hundreds of times per second. With this knowledge, scientists are always on the lookout for new pulsars within and outside our Milky Way galaxy.</p>
<p>In research <a href="https://iopscience.iop.org/article/10.3847/1538-4357/ac61dc">published today in the Astrophysical Journal</a>, we detail our findings on the most luminous radio pulsar ever discovered outside the Milky Way.</p>
<p>This pulsar, named PSR J0523-7125, is located in the Large Magellanic Cloud – one of our closest neighbouring galaxies – and is more than ten times brighter than all other radio pulsars outside the Milky Way. It may be even brighter than those within it.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/gjLk_72V9Bw?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Source: Youtube/NASA.</span></figcaption>
</figure>
<h2>Why wasn’t PSR J0523-7125 discovered before?</h2>
<p>There are more than 3,300 radio pulsars known. Of these, 99% reside within our galaxy. Many were discovered with CSIRO’s famous Parkes radio telescope, <a href="https://blog.csiro.au/parkes-telescope-indigenous-name/">Murriyang</a>, in New South Wales. </p>
<p>About 30 radio pulsars have been found outside our galaxy, in the Magellanic Clouds. So far we don’t know of any in more distant galaxies. </p>
<p>Astronomers search for pulsars by looking for their distinctive repeating signals in radio telescope data. This is a computationally intensive task. It works most of the time, but this method can sometimes fail if the pulsar is unusual: such as very fast, very slow, or (in this case) if the pulse is very wide.</p>
<p>A very wide pulse reduces the signature “flickering” astronomers look for, and can make the pulsar harder to find. We now know PSR J0523-7125 has an extremely wide beam, and thus escaped detection. </p>
<p>The Large Magellanic Cloud has been explored by the Parkes telescope several times over the past 50 years, and yet this pulsar had never been spotted. So how were we able to find it?</p>
<h2>An unusual object emerges in ASKAP data</h2>
<p>Pulsar beams can be highly circularly polarised, which means the electric field of light waves rotate in a circular motion as the waves travel through space. </p>
<p>Such circularly polarised signals are very rare, and usually only emitted from objects with very strong magnetic fields, such as pulsars or dwarf stars.</p>
<p>We wanted to pinpoint unusual pulsars that are hard to identify with traditional methods, so we set out to find them by specifically detecting circularly polarised signals. </p>
<p>Our eyes can’t distinguish between polarised and unpolarised light. But the ASKAP radio telescope, owned and operated by Australia’s national science agency CSIRO, has the equivalent of <a href="https://blog.csiro.au/a-chance-encounter-with-a-pulsar/">polarised sunglasses that can recognise circularly polarised events</a>.</p>
<p>When looking at data from our ASKAP <a href="https://www.vast-survey.org/">Variables and Slow Transients</a> (VAST) survey, an undergraduate student noticed a circular polarised object near the centre of the Large Magellanic Cloud. Moreover, this object changed brightness over the course of several months: another very unusual property that made it unique.</p>
<p>This was unexpected and exciting, since there was no known pulsar or dwarf star at this position. We figured the object must be something new. We observed it with many different telescopes, at different wavelengths, to try and solve the mystery. </p>
<p>Apart from the Parkes (Murriyang) telescope, we used the space-based <a href="https://swift.gsfc.nasa.gov/">Neil Gehrels Swift Observatory</a> (to observe it at X-ray wavelengths) and the <a href="https://www.gemini.edu/">Gemini telescope</a> in Chile (to observe it at infrared wavelengths). Yet we detected nothing. </p>
<p>The object couldn’t be a star, as stars would be visible in optical and infrared light. It was unlikely to be a normal pulsar, as the pulses would have been detected by Parkes. Even the Gemini telescope didn’t provide an answer.</p>
<p>Ultimately we turned to the new, highly sensitive <a href="https://www.sarao.ac.za/science/meerkat/">MeerKAT radio telescope</a> in South Africa, owned and operated by the South African Radio Astronomy Observatory. Observations with MeerKAT revealed the source is indeed a new pulsar, PSR J0523-7125, spinning at a rate of about three rotations per second. </p>
<p>Below you can see the MeerKAT image of the pulsar with polarised “sunglasses” on (left) and off (right). If you move the slider, you’ll notice PSR J0523-7125 is the only bright object when the glasses are on.</p>
<iframe frameborder="0" class="juxtapose" width="100%" height="600" src="https://cdn.knightlab.com/libs/juxtapose/latest/embed/index.html?uid=241ff938-c4fa-11ec-b5bb-6595d9b17862"></iframe>
<p>Our analysis also confirmed its location within the Large Magellanic Cloud, about 160,000 light years away. We were surprised to find PSR J0523-7125 is more than ten times brighter than all other pulsars in that galaxy, and possibly the brightest pulsar ever found.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/fifty-years-ago-jocelyn-bell-discovered-pulsars-and-changed-our-view-of-the-universe-88083">Fifty years ago Jocelyn Bell discovered pulsars and changed our view of the universe</a>
</strong>
</em>
</p>
<hr>
<h2>What new telescopes can do</h2>
<p>The discovery of PSR J0523-7125 demonstrates our ability to find “missing” pulsars using this new technique. </p>
<p>By combining this method with ASKAP’s and MeerKAT’s capabilities, we should be able to discover other types of extreme pulsars – and maybe even other unknown objects that <a href="https://theconversation.com/we-found-a-mysterious-flashing-radio-signal-from-near-the-centre-of-the-galaxy-167802">are hard to explain</a>. </p>
<p>Extreme pulsars are one of the missing pieces in the vast picture of the pulsar population. We’ll need to find more of them before we can truly understand pulsars within the framework of modern physics.</p>
<p>This discovery is just the beginning. ASKAP has now finished its pilot surveys and is expected to launch into full operational capacity later this year. This will pave the way for even more discoveries, when the global <a href="https://www.skatelescope.org/">SKA</a> (square kilometre array) telescope network starts observing in the not too distant future. </p>
<hr>
<p><em>Akncowledgement: We acknowledge the Wajarri Yamatji as the traditional owners of the Murchison Radio-astronomy Observatory site where ASKAP is located, and the Wiradjuri people as the traditional owners of the Parkes Observatory.</em></p><img src="https://counter.theconversation.com/content/180508/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Yuanming Wang receives support from the China Scholarship Council, and as a Graduate Student with the University of Sydney and CSIRO Astronomy and Space Science. </span></em></p><p class="fine-print"><em><span>David Kaplan receives funding from the National Science Foundation.</span></em></p><p class="fine-print"><em><span>Tara Murphy receives funding from the Australian Research Council.</span></em></p>The pulsar PSR J0523-7125 is more than ten times brighter than any other radio pulsar outside the Milky Way.Yuanming Wang, PhD student, University of SydneyDavid Kaplan, Professor of Physics, University of Wisconsin-MilwaukeeTara Murphy, Professor, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1719982021-11-25T16:33:54Z2021-11-25T16:33:54ZWhy it’s location, location, location, even when it comes to galaxy evolution<figure><img src="https://images.theconversation.com/files/433612/original/file-20211124-21-1ynavrc.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C4000%2C4000&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A composite image of the data collected by the ALMA telescope in Chile, showing spiral galaxies in the Virgo Cluster.</span> <span class="attribution"><span class="source">ALMA (ESO/NAOJ/NRAO)/S. Dagnello (NRAO)/T. Brown (VERTICO)</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Star formation — the conversion of gas into stars — is arguably the most important process in the universe. Yet there are regions of space that are so tempestuous, so inhospitable that star formation can be completely halted in the galaxies that reside there. </p>
<p>Astronomers have spent the last 50 years asking: Why is star formation linked to the region of space in which a galaxy lives? And how is it stopped?</p>
<p>A new research project, <a href="https://doi.org/10.3847/1538-4365/ac28f5">the Virgo Environment Traced in Carbon Monoxide (VERTICO) Survey</a>, tries to answer these questions using the world’s most advanced ground-based telescope. The goal is to reveal the influence of so-called galaxy environments on molecular gas, <a href="http://loke.as.arizona.edu/%7Eckulesa/research/overview.html">the raw fuel for star formation</a>, in detail.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/W45H783Q0bU?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The VERTICO survey examines star formation in the Virgo Cluster.</span></figcaption>
</figure>
<h2>A hostile neighbourhood</h2>
<p>VERTICO is focused on a particularly extreme region of space called <a href="http://www.atlasoftheuniverse.com/galgrps/vir.html">the Virgo Cluster</a>, named for its location in the Virgo constellation in the night sky. This cluster contains thousands of galaxies bound together by gravity into one vast superstructure. Galaxy clusters such as this one are the ideal place to observe the effects of environment on star formation.</p>
<p>To understand just how extreme the Virgo Cluster is, it is helpful to place it in the context of our own galactic neighbourhood. The Milky Way resides in a rather <a href="https://doi.org/10.1086/316548">benign group of approximately 80 galaxies</a> that is spread out over five million light-years. In contrast, the Virgo Cluster is more than 1,000 times the mass of the Milky Way, and contains thousands of galaxies in a region of space that is only about three times the size of the Milky Way’s group. </p>
<p>Such a large amount of mass in such a small volume causes extraordinary gravitational forces, which in turn accelerate galaxies to speeds of millions of kilometres per hour and superheat the plasma that permeates the cluster to millions of degrees Celsius. It is these violent conditions that give rise to a class of physical phenomena so powerful they can stop hundreds or even thousands of galaxies from forming stars.</p>
<p><a href="https://nrc.canada.ca/en/stories/whats-killing-galaxies-large-survey-reveals-how-star-formation-shut-down-extreme-regions-universe">VERTICO is a Canadian-led collaboration</a> of international astronomers that used <a href="https://www.almaobservatory.org/en/home/">the Atacama Large Millimeter Array (ALMA) in the Chilean Andes</a> to provide some of the most detailed images ever taken of the star-forming gas in Virgo Cluster galaxies. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/433613/original/file-20211124-17-1p19qb3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="a comma-shaped image of an orange spiral galaxy" src="https://images.theconversation.com/files/433613/original/file-20211124-17-1p19qb3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/433613/original/file-20211124-17-1p19qb3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=540&fit=crop&dpr=1 600w, https://images.theconversation.com/files/433613/original/file-20211124-17-1p19qb3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=540&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/433613/original/file-20211124-17-1p19qb3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=540&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/433613/original/file-20211124-17-1p19qb3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=679&fit=crop&dpr=1 754w, https://images.theconversation.com/files/433613/original/file-20211124-17-1p19qb3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=679&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/433613/original/file-20211124-17-1p19qb3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=679&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Galaxies NGC 4567 and NGC 4568 shown in composite radio data from ALMA with molecular gas in red/orange and optical data from the Hubble Space Telescope with stars in white/blue.</span>
<span class="attribution"><span class="source">(ALMA (ESO/NAOJ/NRAO)/S. Dagnello (NRAO)/T. Brown (VERTICO))</span></span>
</figcaption>
</figure>
<p>With these state-of-the-art data, we are able to identify the physical processes that are affecting how galaxies form their stars by observing their influence on 51 galaxies within the Virgo Cluster.</p>
<p>When we studied the beautiful images captured, we found that, in the Virgo Cluster, external physical processes are capable of reaching far into galaxies to perturb their molecular gas, affecting how stars are born and the galaxy evolves.</p>
<p>Over the next few years, our team will continue to mine this rich resource for insights into how stars form and galaxies grow in extreme environments such as the Virgo Cluster.</p>
<h2>How do galaxies grow?</h2>
<p>A valid question to ask of any scientist is, why does this matter? </p>
<p>From an academic perspective, one of the most satisfying things about astronomy is that simple questions can lead us straight to the frontiers of human understanding. Basic questions such as “Why do stars form?” and “How do galaxies grow?” sit right at the heart of the VERTICO collaboration’s research and will provide the foundation on which the next generation of astronomy will be built.</p>
<p>Astronomy research is a great Canadian, global and human success story. The VERTICO collaboration consists of almost 40 researchers from nine countries, each with their own culture and language. This team has come together to conduct cutting-edge work using the world’s most advanced telescope that has been <a href="https://www.almaobservatory.org/en/about-alma/global-collaboration/">built in Chile using North American, European, Asian and South American technology and expertise</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/433614/original/file-20211124-26-aq186x.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="a striking image of an orange spiral galaxy on a dark background" src="https://images.theconversation.com/files/433614/original/file-20211124-26-aq186x.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/433614/original/file-20211124-26-aq186x.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/433614/original/file-20211124-26-aq186x.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/433614/original/file-20211124-26-aq186x.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/433614/original/file-20211124-26-aq186x.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/433614/original/file-20211124-26-aq186x.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/433614/original/file-20211124-26-aq186x.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Spiral galaxy NGC 4254 is among the thousands of galaxies living and dying by the extreme physical processes in the Virgo Cluster. The galaxy is seen here in radio from ALMA with molecular gas in red/orange and optical from Hubble Space Telescope with stars in white/blue.</span>
<span class="attribution"><span class="source">(ALMA (ESO/NAOJ/NRAO)/S. Dagnello (NRAO)/T. Brown (VERTICO))</span></span>
</figcaption>
</figure>
<p>Scientific projects such as VERTICO drive an exchange of people, ideas and funding between organizations and across borders that is of critical importance to the social, economic and academic fabric of our society.</p><img src="https://counter.theconversation.com/content/171998/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Toby Brown works for the National Research Council Canada, the primary national research and technology organization of the Government of Canada.</span></em></p>Studying the extreme environment of the Virgo Cluster — which comprises thousands of galaxies — helps us learn what factors can affect and start or stop star formation.Toby Brown, Postdoctoral fellow, Astrophysics, McMaster UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1707532021-10-29T04:46:36Z2021-10-29T04:46:36Z60 years after it first gazed at the skies, the Parkes dish is still making breakthroughs<figure><img src="https://images.theconversation.com/files/429275/original/file-20211029-15-198o6ab.jpeg?ixlib=rb-1.1.0&rect=9%2C671%2C6479%2C5136&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">CSIRO</span>, <span class="license">Author provided</span></span></figcaption></figure><p>The CSIRO’s 64-metre Parkes Radio Telescope was commissioned on October 31 1961. At the time it was the most advanced radio telescope in the world, incorporating many innovative features that have since become standard in all large-dish antennas. </p>
<p>Through its early discoveries it quickly became the leading instrument of its kind. Today, 60 years later, it is still arguably the finest single-dish radio telescope in the world. It is still performing world-class science and making discoveries that shape our understanding of the Universe.</p>
<p>The telescope’s origins date back to wartime radar research by the Radiophysics Laboratory, part of the Council for Scientific and Industrial Research (CSIR), the forerunner of the CSIRO. On the Sydney clifftops at Dover Heights, the laboratory developed radar for use in the Pacific theatre. When the second world war ended, the technology was redirected into peaceful applications, including studying radio waves from the Sun and beyond.</p>
<figure class="align-center ">
<img alt="Researchers use the antenna at Dover Heights" src="https://images.theconversation.com/files/429271/original/file-20211029-18-gtm4qf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/429271/original/file-20211029-18-gtm4qf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=601&fit=crop&dpr=1 600w, https://images.theconversation.com/files/429271/original/file-20211029-18-gtm4qf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=601&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/429271/original/file-20211029-18-gtm4qf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=601&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/429271/original/file-20211029-18-gtm4qf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=755&fit=crop&dpr=1 754w, https://images.theconversation.com/files/429271/original/file-20211029-18-gtm4qf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=755&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/429271/original/file-20211029-18-gtm4qf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=755&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Early antennas were much simpler, not to mention smaller.</span>
<span class="attribution"><span class="source">CSIRO</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>In 1946, British physicist Edward “Taffy” Bowen was appointed chief of the Radiophysics Laboratory. He had been one of the brilliant engineers, dubbed “boffins”, who developed radar as part of Britain’s secret prewar military research. The Radiophysics Laboratory had a dedicated radio astronomy group, led by the brilliant Joseph (Joe) Pawsey. Many of the group’s members went on to become leaders in the nascent field of radio astronomy, including Bernie Mills, Chris Christiansen, Paul Wild, Ruby Payne-Scott (the first female radio astronomer), and John Bolton.</p>
<p>While the group’s initial research focused on radio waves from the Sun, Bolton’s attention soon shifted to identifying other sources from farther afield. By the early 1950s, the Dover Heights radar dishes had discovered more than 100 sources of radio emissions from the Milky Way and beyond, including the signals from supernova explosions. These observations established the Radiophysics Laboratory as a world-leading centre of radio astronomy.</p>
<p>By 1954, the technology at Dover Heights was outdated and obsolete, prompting Bowen to initiate the next step for Australian radio astronomy: a state-of-the-art new radio telescope.</p>
<p>He decided the most versatile option was to build a large, fully steerable dish antenna. The eventual price tag was A$1.4 million (A$25.6 million in today’s terms) – far beyond CSIRO’s budget at the time.</p>
<p>The Menzies government agreed to fund the project, provided at least 50% of the money came from the private sector. Using his wartime contacts, Bowen secured A$250,000 each from the Carnegie Corporation and Rockefeller Foundation, plus a range of private Australian donations.</p>
<p>British firm Freeman Fox and Partners produced the detailed design, incorporating suggestions from legendary engineer Barnes Wallis, of “dambusters” fame. Based on the available budget and desired functionality, a diameter of 64 metres was agreed for the dish.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/429264/original/file-20211029-23-nnz6hy.gif?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="1955 design by Barnes Wallis" src="https://images.theconversation.com/files/429264/original/file-20211029-23-nnz6hy.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/429264/original/file-20211029-23-nnz6hy.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=662&fit=crop&dpr=1 600w, https://images.theconversation.com/files/429264/original/file-20211029-23-nnz6hy.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=662&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/429264/original/file-20211029-23-nnz6hy.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=662&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/429264/original/file-20211029-23-nnz6hy.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=832&fit=crop&dpr=1 754w, https://images.theconversation.com/files/429264/original/file-20211029-23-nnz6hy.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=832&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/429264/original/file-20211029-23-nnz6hy.gif?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=832&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">1955 design notes by Barnes Wallis.</span>
<span class="attribution"><span class="source">CSIRO</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The chosen site was near the town of Parkes, about 350km west of Sydney. This location had favourable weather conditions and was free of local radio interference. The local council also enthusiastically offered to cover the cost of some of the earthworks.</p>
<p>In 2020, the local Wiradjuri people <a href="https://blog.csiro.au/parkes-telescope-indigenous-name/">named the telescope Murriyang</a>, a traditional name meaning “Skyworld”.</p>
<p>The telescope’s construction began in September 1959 and was completed just two years later. On October 31 1961, the Governor-General William Sidney, Viscount De l'Isle, officially opened the telescope in a ceremony attended by 500 guests.</p>
<figure class="align-center ">
<img alt="The Parkes dish's opening ceremony" src="https://images.theconversation.com/files/429278/original/file-20211029-26-91kgrk.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/429278/original/file-20211029-26-91kgrk.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=595&fit=crop&dpr=1 600w, https://images.theconversation.com/files/429278/original/file-20211029-26-91kgrk.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=595&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/429278/original/file-20211029-26-91kgrk.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=595&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/429278/original/file-20211029-26-91kgrk.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=748&fit=crop&dpr=1 754w, https://images.theconversation.com/files/429278/original/file-20211029-26-91kgrk.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=748&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/429278/original/file-20211029-26-91kgrk.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=748&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Governor-General (centre) greets guests at the telescope’s 1961 opening ceremony.</span>
<span class="attribution"><span class="source">CSIRO</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Decades of discovery</h2>
<p>John Bolton was appointed the founding director of the telescope. Under his dynamic, decade-long tenure, astronomers made a string of significant discoveries that established the dish as the premier scientific instrument in Australia. </p>
<p>Astronomers revealed the immense magnetic field of our Milky Way galaxy. A few months later, the telescope detected quasars, the most distant known objects in the Universe – a discovery that increased the size of the known Universe tenfold. To cap off a memorable first year, Parkes tracked the very first interplanetary space mission, Mariner 2, when it flew past Venus in December 1962.</p>
<p>In the 1970s, researchers discovered and mapped the immense molecular clouds interspersed through our galaxy. The study of pulsars – rotating stars that emit beams of radio waves, rather like a lighthouse – became a major field of research. Parkes has discovered more pulsars than all other radio observatories combined, including the only known double pulsar system, spotted in 2003. </p>
<p>In the 1990s, the distribution of galaxies was mapped to a distance of 300 million light years, revealing the complex structure of the Universe. More recently, Parkes discovered the first Fast Radio Burst – a short, intense <a href="https://theconversation.com/a-brief-history-what-we-know-so-far-about-fast-radio-bursts-across-the-universe-154381">blast of radio waves</a> created by an as-yet unknown process. The telescope has also been involved in the Search for Extra-Terrestrial Intelligence (SETI), including the ten-year <a href="https://breakthroughinitiatives.org/initiative/1">Breakthrough Listen project</a>, which began in 2016.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/a-brief-history-what-we-know-so-far-about-fast-radio-bursts-across-the-universe-154381">A brief history: what we know so far about fast radio bursts across the universe</a>
</strong>
</em>
</p>
<hr>
<p>To the public, the telescope is perhaps best known for its space tracking, especially its role in the Apollo lunar missions. But it has also supported other significant missions such as NASA’s <a href="https://theconversation.com/australia-is-still-listening-to-voyager-2-as-nasa-confirms-the-probe-is-now-in-interstellar-space-108507">Voyager 2</a>, which flew past Uranus and Neptune in the 1980s and crossed into interstellar space in 2018. In 1986, Parkes was the prime tracking station for the European Giotto mission to Halley’s Comet. And next year, Parkes will track some of the first commercial lunar landers.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/australia-is-still-listening-to-voyager-2-as-nasa-confirms-the-probe-is-now-in-interstellar-space-108507">Australia is still listening to Voyager 2 as NASA confirms the probe is now in interstellar space</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="Parkes dish with the Moon in the background." src="https://images.theconversation.com/files/429268/original/file-20211029-19-1e2zq5n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/429268/original/file-20211029-19-1e2zq5n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=749&fit=crop&dpr=1 600w, https://images.theconversation.com/files/429268/original/file-20211029-19-1e2zq5n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=749&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/429268/original/file-20211029-19-1e2zq5n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=749&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/429268/original/file-20211029-19-1e2zq5n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=941&fit=crop&dpr=1 754w, https://images.theconversation.com/files/429268/original/file-20211029-19-1e2zq5n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=941&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/429268/original/file-20211029-19-1e2zq5n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=941&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Parkes tracking the Apollo Moon mission in 1969.</span>
<span class="attribution"><span class="source">CSIRO</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Originally intended to operate for 20 years, the telscope’s longevity is a result of constant upgrades. Recent improvements include a new ultra-wideband receiver that can scan a huge range of radio frequencies, and CSIRO-developed “phased array feeds” (PAFs) that allow the telescope to observe up to 36 points in the sky at once. Work is now under way on a cryogenically cooled PAF that, when installed in 2022, will double this number. With these upgrades in place, a single receiver can be used to deliver more than 90% of current Parkes operations.</p>
<figure class="align-center ">
<img alt="Construction workers building the dish" src="https://images.theconversation.com/files/429273/original/file-20211029-25-1ocnr6f.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/429273/original/file-20211029-25-1ocnr6f.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=570&fit=crop&dpr=1 600w, https://images.theconversation.com/files/429273/original/file-20211029-25-1ocnr6f.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=570&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/429273/original/file-20211029-25-1ocnr6f.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=570&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/429273/original/file-20211029-25-1ocnr6f.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=716&fit=crop&dpr=1 754w, https://images.theconversation.com/files/429273/original/file-20211029-25-1ocnr6f.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=716&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/429273/original/file-20211029-25-1ocnr6f.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=716&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Construction took just two years.</span>
<span class="attribution"><span class="source">CSIRO</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>It’s hard to say how long the Parkes dish will continue to work. It depends on future upgrades and whether the telescope’s structure remains in good working order. But astronomers will always have a need for a large single-dish antenna.</p>
<p>Parkes has maintained its world-leading position in radio astronomy by constantly adapting to meet new requirements. Today it stands as an icon of Australian science and achievement. Sixty years after it first trained its eye on the sky, the future still looks bright at Parkes.</p><img src="https://counter.theconversation.com/content/170753/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>John Sarkissian does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>After six decades during which it tracked lunar missions, spotted distant pulsars and quasars, and even expanded our concept of the size of the Universe, the Parkes telescope is still going strong.John Sarkissian, Operations Scientist, CSIROLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1700962021-10-22T01:29:51Z2021-10-22T01:29:51ZCurious Kids: why do we see the ‘sky’ during the day, but the galaxy at night?<figure><img src="https://images.theconversation.com/files/427402/original/file-20211020-19-1iq9frn.jpeg?ixlib=rb-1.1.0&rect=155%2C5%2C3838%2C1197&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Milky_Way#/media/File:Milky_Way_Arch.jpg">Bruno Gilli/ESO/Wiki Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><blockquote>
<p>Why do we see the sky during the day, but the galaxy at night? — Gary, age 9, Auckland </p>
</blockquote>
<p><a href="https://theconversation.com/au/topics/curious-kids-36782"><img src="https://images.theconversation.com/files/291898/original/file-20190911-190031-enlxbk.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=90&fit=crop&dpr=1" width="100%"></a></p>
<p>Hi Gary! Thank you for this great question. </p>
<p>To put it simply, the reason the sky looks different to us between daytime and nighttime is mostly because of our atmosphere. </p>
<p>The atmosphere surrounds Earth, and extends from the ground to outer space. It’s made of different gases including oxygen (which keeps us alive as we breathe it in), carbon dioxide (which we breathe out), methane (which is also in our farts), nitrogen and argon. </p>
<p>All these gases, as well as all solids and liquids, are made of molecules. Molecules are collections of atoms which are much too small for us to see, but are the basic building blocks of everything that exists. Importantly, different molecules have different combinations of atoms and come in different sizes.</p>
<p>A molecule’s size plays a role in how the molecule interacts with light. Light from the Sun isn’t one colour — it’s made up of all the colours of the rainbow (which is why we see a rainbow when light behaves in a certain way). </p>
<p>Some of the molecules in Earth’s atmosphere are just the right size that the blue part of the light from the Sun bounces off them, scattering in different directions. </p>
<p>So when we look towards the Sun during the day (remembering that you should never look directly <em>at</em> the Sun), we see rays of light that have come from the Sun straight down to us. </p>
<p>But when we look away from the Sun we see the blue light rays scattering from the part of the atmosphere we are looking at. That’s why the sky is so bright — and blue — during the day.</p>
<h2>The galaxy at night</h2>
<p>At night we see stars in a dark sky, and these stars make up our galaxy, the Milky Way. The Milky Way is made of a huge number of stars, including the Sun. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/427950/original/file-20211022-13-1yw1v30.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Galaxy sky at night" src="https://images.theconversation.com/files/427950/original/file-20211022-13-1yw1v30.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/427950/original/file-20211022-13-1yw1v30.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/427950/original/file-20211022-13-1yw1v30.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/427950/original/file-20211022-13-1yw1v30.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/427950/original/file-20211022-13-1yw1v30.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/427950/original/file-20211022-13-1yw1v30.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/427950/original/file-20211022-13-1yw1v30.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Milky Way contains all the stars in our galaxy, and each of these stars might have orbiting planets, just like the Earth orbits the Sun.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>Compared with other stars, the Sun actually isn’t that bright, but it looks very bright to us because it’s much closer to Earth than other stars are.</p>
<p>At night, when your side of Earth is facing away from the Sun, the only light that reaches you is from other stars. This starlight also scatters off molecules in the atmosphere, but as there’s less of it, not much scattering goes on.</p>
<p>This is why, at night when we’re facing away from the Sun, we don’t see the same thing as when we are facing the Sun during the day. Instead, we can look through the atmosphere and beyond at the big, dark expanse of space around us and the many, many faraway stars in our galaxy.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-how-does-the-sun-make-such-pretty-colours-at-sunsets-and-sunrises-151278">Curious Kids: how does the Sun make such pretty colours at sunsets and sunrises?</a>
</strong>
</em>
</p>
<hr>
<h2>The sky on other planets</h2>
<p>Other planets in our Solar System have different molecules in their atmosphere compared with Earth, which means their skies look different during the day and night.</p>
<p>The atmosphere on Venus, for example, is so thick you would never see the Sun — not even during the day when you were facing towards it. The stars are not visible at night, either. </p>
<p>Astronauts who are above our atmosphere, such as on the International Space Station or on the Moon, don’t see the bright blue sky we see on Earth. Instead, they see the Sun as a large nearby star against a black sky. </p>
<p>And they can see the galaxy all the time. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/427405/original/file-20211020-19033-1cf526q.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/427405/original/file-20211020-19033-1cf526q.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/427405/original/file-20211020-19033-1cf526q.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/427405/original/file-20211020-19033-1cf526q.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/427405/original/file-20211020-19033-1cf526q.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/427405/original/file-20211020-19033-1cf526q.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/427405/original/file-20211020-19033-1cf526q.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/427405/original/file-20211020-19033-1cf526q.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Astronauts onboard the International Space Station can get a great view of the Sun in ‘starburst’ mode over Earth.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/content/sun-over-earths-horizon">NASA</a></span>
</figcaption>
</figure><img src="https://counter.theconversation.com/content/170096/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The sky on other planets doesn’t look the same as the sky on Earth does. And that’s because of the different gases in Earth’s atmosphere.Hannah Schunker, Lecturer of Physics, University of NewcastleDavid Pontin, Associate Professor of Physics, University of NewcastleLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1678022021-10-12T19:12:42Z2021-10-12T19:12:42ZWe found a mysterious flashing radio signal from near the centre of the galaxy<figure><img src="https://images.theconversation.com/files/425181/original/file-20211007-21-yk2cki.png?ixlib=rb-1.1.0&rect=0%2C8%2C1917%2C1069&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Sebastian Zentilomo/University of Sydney</span>, <span class="license">Author provided</span></span></figcaption></figure><p>In early 2020, we <a href="https://doi.org/10.3847/1538-4357/ac2360">detected an unusual radio signal</a> coming from somewhere near the centre of our galaxy. The signal blinked on and off, growing 100 times brighter and dimmer over time.</p>
<p>What’s more, the radio waves in the signal had an uncommon “circular polarisation”, which means the electric field in the radio waves spirals around as the waves travel through space.</p>
<p>We first spotted the signal using the <a href="https://www.csiro.au/en/about/facilities-collections/ATNF/ASKAP-radio-telescope">Australian Square Kilometre Array Pathfinder Telescope (ASKAP)</a>, then followed up with other telescopes around the world and in space. Despite our best efforts, we are still unable to work out exactly what produced these mysterious radio waves.</p>
<h2>A strange signal from the heart of the Milky Way</h2>
<p>We have been surveying the sky with ASKAP throughout 2020 and 2021 in search of unusual new objects, in a project called the <a href="https://vast-survey.org/">Variables and Slow Transients (VAST)</a> survey. </p>
<p>Most things astronomers see in outer space are fairly stable and don’t change much on human time scales. That’s why objects that do change (known as variables) or appear and disappear (known as transients) are so interesting.</p>
<p>Transients are usually connected with some of the most energetic and violent events in the Universe, such as the death of massive stars. The past decade has seen thousands of transients discovered at optical and X-ray wavelengths, but radio wavelengths are largely untapped. </p>
<p>When we looked towards the centre of our galaxy (the Milky Way), we found a source we called ASKAP J173608.2-321635 (this catchy name comes from its coordinates in the sky). This object was unique in that it started out invisible, became bright, faded away, and then reappeared. This behaviour was extraordinary.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/422308/original/file-20210921-25-1fog93f.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/422308/original/file-20210921-25-1fog93f.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=586&fit=crop&dpr=1 600w, https://images.theconversation.com/files/422308/original/file-20210921-25-1fog93f.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=586&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/422308/original/file-20210921-25-1fog93f.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=586&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/422308/original/file-20210921-25-1fog93f.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=736&fit=crop&dpr=1 754w, https://images.theconversation.com/files/422308/original/file-20210921-25-1fog93f.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=736&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/422308/original/file-20210921-25-1fog93f.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=736&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">ASKAP image of the Galactic Centre region. The small insets show the source turning off and on in images from the MeerKAT telescope.</span>
<span class="attribution"><span class="source">Author provided</span></span>
</figcaption>
</figure>
<p>As well as changing over time, the signal was circularly polarised. Our eyes cannot distinguish between polarised and unpolarised light, but ASKAP has the equivalent of <a href="https://blog.csiro.au/a-chance-encounter-with-a-pulsar/">polaroid sunglasses for radio waves</a>. </p>
<p>Polarised radio sources are extremely rare: we might find fewer than ten circularly polarised sources out of thousands. Almost all of them are sources we understand well, such as pulsars (the rapidly rotating, highly magnetised remnants of exploded stars) or <a href="https://spaceaustralia.com/feature/radio-stars-emerge-askaps-survey-southern-skies">highly magnetised red dwarf stars</a>.</p>
<h2>Finding more evidence</h2>
<p>Investigating a new astronomical object is a bit like a detective job. We need evidence to determine what it is. </p>
<p>Based on our ASKAP data, we thought the new object might be a pulsar or a flaring star: both types of object can be polarised, and change in brightness. However, we needed to find more clues.</p>
<p>We next observed the source with the <a href="https://www.csiro.au/en/about/facilities-collections/atnf/parkes-radio-telescope">Parkes radio telescope</a> in New South Wales to decide whether it was a pulsar. However, these observations yielded nothing. </p>
<p>We then tried the more sensitive <a href="https://www.sarao.ac.za/science/meerkat/">MeerKAT radio telescope</a> in South Africa. Because the signal was intermittent, we observed it for 15 minutes every few weeks, hoping we would see it again. Luckily, the signal returned, but the behaviour of the source was now dramatically different. The source disappeared in the course of a single day, even though it had lasted for weeks in our previous ASKAP observations.</p>
<figure class="align-center ">
<img alt="radio lightcurve" src="https://images.theconversation.com/files/422309/original/file-20210921-23-tcoink.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/422309/original/file-20210921-23-tcoink.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/422309/original/file-20210921-23-tcoink.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/422309/original/file-20210921-23-tcoink.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/422309/original/file-20210921-23-tcoink.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=425&fit=crop&dpr=1 754w, https://images.theconversation.com/files/422309/original/file-20210921-23-tcoink.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=425&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/422309/original/file-20210921-23-tcoink.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=425&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Radio lightcurve showing how ASKAP J173608.2-321635 varies with time.</span>
<span class="attribution"><span class="source">Author provided</span></span>
</figcaption>
</figure>
<p>It is always a good idea to investigate from multiple perspectives. Telescopes working at other wavelengths can serve as another pair of eyes to help us find new clues. </p>
<p>After the MeerKAT detection, we searched for the source in X-rays (using the space-based Neil Gehrels Swift Observatory and Chandra X-ray Observatory) and infrared (using the Gemini telescope in Chile). However, we saw nothing.</p>
<h2>Still a mystery</h2>
<p>We have observed this strange object at multiple wavelengths using telescopes on three continents and in space. What can we say about what it actually is?</p>
<p>Can it be a star? It seems unlikely because stars also emit much of their light in the optical and infrared (like the Sun), but we detect nothing at these wavelengths.</p>
<p>Can it be a pulsar? Like our signal, pulsars produce polarised radio waves and can vary dramatically in brightness. But the characteristic of pulsars is rapid pulses betweem milliseconds to seconds long, and we did not detect these with Parkes or MeerKAT.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/fifty-years-ago-jocelyn-bell-discovered-pulsars-and-changed-our-view-of-the-universe-88083">Fifty years ago Jocelyn Bell discovered pulsars and changed our view of the universe</a>
</strong>
</em>
</p>
<hr>
<p>Is the source’s proximity to the centre of our galaxy a clue? Over the past 15 years, a number of intriguing radio sources have been discovered toward the Galactic centre (including one dubbed the “cosmic burper”). We don’t know what they are, but they are imaginatively called <a href="https://en.wikipedia.org/wiki/GCRT_J1745%E2%88%923009">Galactic Center Radio Transients</a> (GCRTs). </p>
<p>Are they related to ASKAP J173608.2-321635? There are some similarities, but there are also differences. And even the known GCRTs exhibit diversity, and may not share a common origin. So our signal is still a mystery.</p>
<p>We will keep observing this source in new ways. It is just the first of many unusual transient sources that we expect to find with the powerful ASKAP array, and it gives a hint of the future of radio astronomy. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/wtf-newly-discovered-ghostly-circles-in-the-sky-cant-be-explained-by-current-theories-and-astronomers-are-excited-142812">'WTF?': newly discovered ghostly circles in the sky can't be explained by current theories, and astronomers are excited</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/167802/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ziteng Wang received support from University of Sydney International Scholarship, and as a Graduate Student with CSIRO Space and Astronomy.</span></em></p><p class="fine-print"><em><span>David Kaplan receives funding from the National Science Foundation.</span></em></p><p class="fine-print"><em><span>Tara Murphy works for The University of Sydney. She receives funding from the Australian Research Council. </span></em></p>Fluctuating radio waves that appear to come from near the heart of the Milky Way are a new puzzle for astronomers.Ziteng Wang, PhD researcher, University of SydneyDavid Kaplan, Associate professor of Physics, University of Wisconsin-MilwaukeeTara Murphy, Professor, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1653702021-09-20T12:32:32Z2021-09-20T12:32:32ZHow many stars are there in space?<figure><img src="https://images.theconversation.com/files/413827/original/file-20210729-21-neazw1.jpg?ixlib=rb-1.1.0&rect=10%2C0%2C3356%2C2624&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Astronomers have found a way to estimate the number of stars in the universe.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/open-star-cluster-royalty-free-image/86804879">Comstock Images via Getty Images</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
<hr>
<blockquote>
<p><strong>Exactly how many stars are in space? – MeeSong, Brookline, Massachusetts</strong></p>
</blockquote>
<hr>
<p>Look up at the sky on a clear night, and you’ll see thousands of stars – about 6,000 or so. </p>
<p>But that’s only a tiny fraction of all the stars out there. The rest are too far away for us to see them. </p>
<figure class="align-center ">
<img alt="A photograph of the Sun." src="https://images.theconversation.com/files/414045/original/file-20210801-15-k97bpt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/414045/original/file-20210801-15-k97bpt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/414045/original/file-20210801-15-k97bpt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/414045/original/file-20210801-15-k97bpt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/414045/original/file-20210801-15-k97bpt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/414045/original/file-20210801-15-k97bpt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/414045/original/file-20210801-15-k97bpt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Sun is a star, the closest one to us – 93 million miles away.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/blue-sky-and-white-clouds-background-clouds-in-the-royalty-free-image/1251306427?adppopup=true">Roman Studio/Moment via Getty Images</a></span>
</figcaption>
</figure>
<h2>The universe, galaxies, stars</h2>
<p>Yet astronomers <a href="http://www.astrojack.com/">like me</a> have figured out how to estimate the total number of stars <a href="https://exoplanets.nasa.gov/what-is-an-exoplanet/what-is-the-universe/">in the universe, which is everything that exists</a>.</p>
<p>Scattered throughout the universe are <a href="https://science.nasa.gov/astrophysics/focus-areas/what-are-galaxies">galaxies</a> – clusters of stars, planets, gas and dust bunched together. </p>
<p>Like people, galaxies are diverse. They come in different sizes and shapes.</p>
<p>Earth is in the <a href="https://imagine.gsfc.nasa.gov/science/objects/milkyway1.html">Milky Way</a>, a spiral galaxy; its stars cluster in spiral arms that swirl around the galaxy’s center. </p>
<p>Other galaxies are <a href="https://www.nasa.gov/multimedia/imagegallery/image_feature_299.html">elliptical</a> – kind of egg-shaped – and some are <a href="https://www.nasa.gov/image-feature/goddard/2019/hubble-captures-elusive-irregular-galaxy">irregular</a>, with a variety of shapes. </p>
<figure class="align-center ">
<img alt="An artist's concept of the swirling spiral arms of our Milky Way galaxy." src="https://images.theconversation.com/files/413225/original/file-20210727-24-1fdgku8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/413225/original/file-20210727-24-1fdgku8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/413225/original/file-20210727-24-1fdgku8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/413225/original/file-20210727-24-1fdgku8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/413225/original/file-20210727-24-1fdgku8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/413225/original/file-20210727-24-1fdgku8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/413225/original/file-20210727-24-1fdgku8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Artist’s concept of a face-on look at the Milky Way. Note the spiral arms.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/images/content/188404main_hurt_Milky_Way_2005-590_lg.jpg">NASA/JPL</a></span>
</figcaption>
</figure>
<figure class="align-center ">
<img alt="A nighttime photograph taken at Utah's Canyonlands National Park, looking skyward and revealing thousands of stars in the Milky Way." src="https://images.theconversation.com/files/413203/original/file-20210726-25-138wsm8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/413203/original/file-20210726-25-138wsm8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/413203/original/file-20210726-25-138wsm8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/413203/original/file-20210726-25-138wsm8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/413203/original/file-20210726-25-138wsm8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/413203/original/file-20210726-25-138wsm8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/413203/original/file-20210726-25-138wsm8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">From Canyonlands National Park in Utah, a view of a small part of the Milky Way.</span>
<span class="attribution"><a class="source" href="https://www.nps.gov/media/photo/gallery-item.htm?pg=1908159&id=286169fc-2bab-40e0-bf8b-a13b5170aeb3&gid=2ADECB87-1DD8-B71B-0B09BD0B18C96667">National Park Service/Emily Ogden</a></span>
</figcaption>
</figure>
<h2>Counting the galaxies</h2>
<p>Before calculating the number of stars in the universe, astronomers first have to estimate the number of galaxies.</p>
<p>To do that, they take very detailed pictures of small parts of the sky and count all the galaxies they see in those pictures. </p>
<p>That number is then multiplied by the number of pictures needed to photograph the whole sky.</p>
<p>The answer: There are approximately 2,000,000,000,000 galaxies in the universe – that’s 2 trillion.</p>
<figure class="align-center ">
<img alt="15,000 galaxies appear as small dots and blots in this NASA photograph of the nighttime sky." src="https://images.theconversation.com/files/420897/original/file-20210913-23828-1xbipdi.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/420897/original/file-20210913-23828-1xbipdi.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=530&fit=crop&dpr=1 600w, https://images.theconversation.com/files/420897/original/file-20210913-23828-1xbipdi.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=530&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/420897/original/file-20210913-23828-1xbipdi.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=530&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/420897/original/file-20210913-23828-1xbipdi.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=667&fit=crop&dpr=1 754w, https://images.theconversation.com/files/420897/original/file-20210913-23828-1xbipdi.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=667&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/420897/original/file-20210913-23828-1xbipdi.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=667&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">15,000 galaxies appear as small dots and blots in this NASA photograph of the nighttime sky. Each galaxy contains billions of stars.</span>
<span class="attribution"><a class="source" href="https://astrobiology.nasa.gov/news/15000-galaxies-in-one-image/">NASA/ESA/P.Oesch/M.Montes</a></span>
</figcaption>
</figure>
<h2>Counting the stars</h2>
<p>Astronomers don’t know exactly how many stars are in each of those 2 trillion galaxies. Most are so distant, there’s no way to tell precisely.</p>
<p>But we can make a good guess at the number of stars in our own Milky Way. Those stars are diverse, too, and come in a wide variety of sizes and colors. </p>
<p>Our Sun, a white star, is medium-size, medium-weight and medium-hot: 27 million degrees Fahrenheit at its center (15 million degrees Celsius).</p>
<p>Bigger, heavier and hotter stars tend to be blue, like <a href="https://www.nasa.gov/mission_pages/spitzer/multimedia/pia16611.html">Vega</a> in the constellation Lyra. Smaller, lighter and dimmer stars are usually red, like <a href="https://www.nasa.gov/content/goddard/hubbles-new-shot-of-proxima-centauri-our-nearest-neighbor/#.YQHMdY5KjD4">Proxima Centauri</a>. Except for the Sun, it’s the closest star to us.</p>
<figure class="align-center ">
<img alt="A red dwarf star." src="https://images.theconversation.com/files/413617/original/file-20210728-21-zy29ie.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/413617/original/file-20210728-21-zy29ie.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=464&fit=crop&dpr=1 600w, https://images.theconversation.com/files/413617/original/file-20210728-21-zy29ie.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=464&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/413617/original/file-20210728-21-zy29ie.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=464&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/413617/original/file-20210728-21-zy29ie.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=583&fit=crop&dpr=1 754w, https://images.theconversation.com/files/413617/original/file-20210728-21-zy29ie.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=583&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/413617/original/file-20210728-21-zy29ie.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=583&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Artist’s concept of a red dwarf star with an exoplanet in orbit. About two-thirds of the stars in the Milky Way are red dwarfs. Exoplanet is the name for worlds outside our solar system.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/image-feature/jpl/pia21473/flaring-red-dwarf-star">NASA/ESA/G.Bacon/STScI</a></span>
</figcaption>
</figure>
<h2>An incredible number</h2>
<p>Red, white and blue stars give off different amounts of light. By measuring that starlight – specifically, its color and brightness – astronomers can estimate how many stars our galaxy holds.</p>
<p>With that method, they discovered the Milky Way has about 100 billion stars – 100,000,000,000. </p>
<p>Now the next step. Using the Milky Way as our model, we can multiply the number of stars in a typical galaxy (100 billion) by the number of galaxies in the universe (2 trillion). </p>
<p>The answer is an absolutely astounding number. There are approximately 200 billion trillion stars in the universe. Or, to put it another way, 200 sextillion. </p>
<p>That’s 200,000,000,000,000,000,000,000! </p>
<p>The number is so big, it’s hard to imagine. But try this: It’s about 10 times the number of cups of water in all the oceans of Earth.</p>
<p>Think about that the next time you’re looking at the night sky – and then wonder about <a href="https://theconversation.com/are-there-any-planets-outside-of-our-solar-system-164062">what might be happening on the trillions of worlds</a> orbiting all those stars.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/MX3PIkbTQwQ?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">NASA video. Our Milky Way galaxy: How big is space?</span></figcaption>
</figure>
<hr>
<p><em>Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>. Please tell us your name, age and the city where you live.</em></p>
<p><em>And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.</em></p><img src="https://counter.theconversation.com/content/165370/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Brian Jackson receives funding from NASA. </span></em></p>Scientists have a good estimate on the staggering number of stars in the universe.Brian Jackson, Associate Professor of Astronomy, Boise State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1675162021-09-15T12:16:51Z2021-09-15T12:16:51ZJames Webb Space Telescope: An astronomer on the team explains how to send a giant telescope to space – and why<figure><img src="https://images.theconversation.com/files/420973/original/file-20210914-15-1g3wm0u.jpg?ixlib=rb-1.1.0&rect=29%2C0%2C2959%2C2109&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The James Webb Space Telescope is the biggest orbital telescope ever built and is scheduled to be launched into space on Dec. 18, 2021.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/nasawebbtelescope/33433274343/in/album-72157711864921848/">NASA/Desiree Stover</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>The James Webb Space Telescope was launched into space on Dec. 25, 2021, and with it, astronomers hope to find the first galaxies to form in the universe, will search for Earthlike atmospheres around other planets and accomplish many other scientific goals. </p>
<p>I am <a href="https://profiles.arizona.edu/person/mrieke">an astronomer</a> and the <a href="https://jwst.nasa.gov/content/meetTheTeam/people/riekeMarcia.html">principal investigator for the Near Infrared Camera</a> – or <a href="https://www.jwst.nasa.gov/content/observatory/instruments/nircam.html">NIRCam</a> for short – aboard the Webb telescope. I have participated in the development and testing for both my camera and the telescope as a whole. </p>
<p>To see deep into the universe, the telescope has a very large mirror and must be kept extremely cold. But getting a fragile piece of equipment like this to space is no simple task. There have been many challenges my colleagues and I have had to overcome to design, test and soon launch and align the most powerful space telescope ever built.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/420980/original/file-20210914-15-gztf6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A gold section of the mirror with the sensors extended out in front of the mirror." src="https://images.theconversation.com/files/420980/original/file-20210914-15-gztf6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/420980/original/file-20210914-15-gztf6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=446&fit=crop&dpr=1 600w, https://images.theconversation.com/files/420980/original/file-20210914-15-gztf6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=446&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/420980/original/file-20210914-15-gztf6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=446&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/420980/original/file-20210914-15-gztf6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=561&fit=crop&dpr=1 754w, https://images.theconversation.com/files/420980/original/file-20210914-15-gztf6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=561&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/420980/original/file-20210914-15-gztf6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=561&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">In order to detect the most distant and oldest galaxies, the telescope needs to be huge and kept extremely cold.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/nasawebbtelescope/48474089192/in/album-72157711864057113/">NASA/Chris Gunn</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Young galaxies and alien atmospheres</h2>
<p>The Webb telescope has a mirror over 20 feet across, a tennis-court sized sun shade to block solar radiation and <a href="https://www.jwst.nasa.gov/content/about/faqs/facts.html">four separate camera and sensor systems to collect the data</a>.</p>
<p>It works kind of like a satellite dish. Light from a star or galaxy will enter the mouth of the telescope and bounce off the primary mirror toward the four sensors: <a href="https://www.jwst.nasa.gov/content/observatory/instruments/nircam.html">NIRCam</a>, which takes images in the near infrared; the <a href="https://jwst.nasa.gov/content/observatory/instruments/nirspec.html">Near Infrared Spectrograph</a>, which can split the light from a selection of sources into their constituent colors and measures the strength of each; the <a href="https://jwst.nasa.gov/content/observatory/instruments/miri.html">Mid-Infrared Instrument</a>, which takes images and measures wavelengths in the middle infrared; and the <a href="https://jwst.nasa.gov/content/observatory/instruments/fgs.html">Near Infrared Imaging Slitless Spectrograph</a>, which splits and measures the light of anything scientists point the satellite at. </p>
<p>This design will allow scientists to study how stars form in the Milky Way and the atmospheres of planets outside the Solar System. It may even be possible to figure out the composition of these atmospheres. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/420991/original/file-20210914-19-1sfzdgw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A complicated, gold-plated, hexagonal instrument standing on four silvery legs." src="https://images.theconversation.com/files/420991/original/file-20210914-19-1sfzdgw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/420991/original/file-20210914-19-1sfzdgw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=396&fit=crop&dpr=1 600w, https://images.theconversation.com/files/420991/original/file-20210914-19-1sfzdgw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=396&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/420991/original/file-20210914-19-1sfzdgw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=396&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/420991/original/file-20210914-19-1sfzdgw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=497&fit=crop&dpr=1 754w, https://images.theconversation.com/files/420991/original/file-20210914-19-1sfzdgw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=497&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/420991/original/file-20210914-19-1sfzdgw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=497&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The NIRCam, seen here, will measure infrared light from extremely distant and old galaxies.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/nasawebbtelescope/9415131365/in/photolist-fmf3UY-fkZ1x8-EhkNDe-ejcWcJ-efMxLE-8kkzhW-o56Mza-mCPCtX-ejcW93-fmd8GA-ej7cDM-mwwpu9-mhqW1z-fjmkiu-mhqcca-mwvC6z-fj3xBn-oE2Vqt-fjhJoq-8BFiRP-JMjqRn-z4QocM-DS62eM-bQR3J8-QrgMDK-msJYwx-fj3xva-8BFiQe-mD44oa-oE2Vrv-mGKH6V-fjYuZE-qaR5ki-qs7Aht-2kJdtfv-pviffL-2kJ9HFz-2kJdX8k-2kJ9HJR-Nw7FDp-ER9JHT-qNSDpw">NASA/Chris Gunn</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Ever since Edwin Hubble proved that distant galaxies are just like the Milky Way, astronomers have asked: How old are the oldest galaxies? How did they first form? And how have they changed over time? The Webb telescope was originally dubbed the <a href="https://www.stsci.edu/files/live/sites/www/files/home/news/newsletters/_documents/2002-volume019-issue04.pdf">“First Light Machine”</a> because it is designed to answer these very questions. </p>
<p>One of the main goals of the telescope is to study distant galaxies close to the edge of observable universe. It takes billions of years for the light from these galaxies to cross the universe and reach Earth. I estimate that images my colleagues and I will collect with NIRCam could show protogalaxies that formed a mere 300 million years after the Big Bang – when they were just 2% of their current age. </p>
<p>Finding the first aggregations of stars that formed after the Big Bang is a daunting task for a simple reason: These protogalaxies are very far away and so appear to be very faint.</p>
<p>Webb’s mirror is made of 18 separate segments and can collect more than <a href="https://www.jwst.nasa.gov/content/about/comparisonWebbVsHubble.html">six times as much light as the Hubble Space Telescope mirror</a>. Distant objects also appear to be very small, so the telescope must be able to focus the light as tightly as possible.</p>
<p>The telescope also has to cope with another complication: Since <a href="https://doi.org/10.1073/pnas.1424299112">the universe is expanding</a>, the galaxies that scientists will study with the Webb telescope are moving away from Earth, and the Doppler effect comes into play. Just like the pitch of an ambulance’s siren shifts down and becomes deeper when it passes and starts moving away from you, the wavelength of light from distant galaxies shifts down from visible light to infrared light. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/420983/original/file-20210914-17-1js8d4r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A golden mirror with multiple layers of silvery material spread out beneath it." src="https://images.theconversation.com/files/420983/original/file-20210914-17-1js8d4r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/420983/original/file-20210914-17-1js8d4r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=458&fit=crop&dpr=1 600w, https://images.theconversation.com/files/420983/original/file-20210914-17-1js8d4r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=458&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/420983/original/file-20210914-17-1js8d4r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=458&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/420983/original/file-20210914-17-1js8d4r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=575&fit=crop&dpr=1 754w, https://images.theconversation.com/files/420983/original/file-20210914-17-1js8d4r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=575&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/420983/original/file-20210914-17-1js8d4r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=575&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The five layers of silvery material underneath the gold mirror are a sunshield that will reflect light and heat to keep the sensors incredibly cold.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/nasawebbtelescope/48936479373/in/album-72157711864057113/">NASA/Chris Gunn</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Webb detects infrared light – it is essentially a giant heat telescope. To “see” faint galaxies in infrared light, the telescope needs to be exceptionally cold or else all it would see would be its own infrared radiation. This is where the heat shield comes in. The shield is made of a thin plastic coated with aluminum. It is five layers thick and measures 46.5 feet (17.2 meters) by 69.5 feet (21.2 meters) and will <a href="https://www.jwst.nasa.gov/content/observatory/sunshield.html">keep the mirror and sensors at minus 390 degrees Fahrenheit (minus 234 Celsius)</a>.</p>
<p>The Webb telescope is an incredible feat of engineering, but how does one get such a thing safely to space and guarantee that it will work?</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/420988/original/file-20210914-17-1gpyesh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="The assembled telescope being wheeled out of a large chamber." src="https://images.theconversation.com/files/420988/original/file-20210914-17-1gpyesh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/420988/original/file-20210914-17-1gpyesh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/420988/original/file-20210914-17-1gpyesh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/420988/original/file-20210914-17-1gpyesh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/420988/original/file-20210914-17-1gpyesh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/420988/original/file-20210914-17-1gpyesh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/420988/original/file-20210914-17-1gpyesh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Engineers and scientists tested the entire telescope in an an extremely cold, low-pressure cryogenic vacuum chamber.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/nasawebbtelescope/25003831358/in/album-72157711864057113/">NASA/Chris Gunn</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Test and rehearse</h2>
<p>The James Webb Space Telescope will orbit a <a href="https://jwst-docs.stsci.edu/jwst-observatory-hardware/jwst-orbit">million miles from Earth</a> – about 4,500 times more distant than the International Space Station and much too far to be serviced by astronauts.</p>
<p>Over the past 12 years, the team has tested the telescope and instruments, shaken them to simulate the rocket launch and tested them again. Everything has been cooled and tested under the extreme operating conditions of orbit. I will never forget when my team was in Houston testing the NIRCam using a chamber designed for the Apollo lunar rover. It was the first time that my camera detected light that had bounced off the telescope’s mirror, and we couldn’t have been happier – even though Hurricane Harvey was fighting us outside. </p>
<figure class="align-center ">
<img alt="People sitting at desks using computers." src="https://images.theconversation.com/files/420986/original/file-20210914-25-5rdqpq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/420986/original/file-20210914-25-5rdqpq.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=398&fit=crop&dpr=1 600w, https://images.theconversation.com/files/420986/original/file-20210914-25-5rdqpq.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=398&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/420986/original/file-20210914-25-5rdqpq.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=398&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/420986/original/file-20210914-25-5rdqpq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/420986/original/file-20210914-25-5rdqpq.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/420986/original/file-20210914-25-5rdqpq.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Rehearsals and training at the Space Telescope Science Institute are critical to make sure that the assembly process goes smoothly and any unexpected anomalies can be dealt with.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/nasawebbtelescope/45061379081/in/album-72157701979601735/">NASA/STScI</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>After testing came the rehearsals. The telescope will be controlled remotely by commands sent over a radio link. But because the telescope will be so far away – it takes six seconds for a signal to go one way – there is no real-time control. So for the past three years, my team and I have been going to the <a href="https://www.stsci.edu/">Space Telescope Science Institute</a> in Baltimore and running rehearsal missions on a simulator covering everything from launch to routine science operations. The team even has practiced dealing with potential problems that the test organizers throw at us and cutely call “anomalies.” </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/420987/original/file-20210914-13-1jli4qz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A tall, rectangular bundle of silvery material, gold mirrors and metal framing." src="https://images.theconversation.com/files/420987/original/file-20210914-13-1jli4qz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/420987/original/file-20210914-13-1jli4qz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=750&fit=crop&dpr=1 600w, https://images.theconversation.com/files/420987/original/file-20210914-13-1jli4qz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=750&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/420987/original/file-20210914-13-1jli4qz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=750&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/420987/original/file-20210914-13-1jli4qz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=942&fit=crop&dpr=1 754w, https://images.theconversation.com/files/420987/original/file-20210914-13-1jli4qz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=942&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/420987/original/file-20210914-13-1jli4qz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=942&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">To fit inside a rocket, the telescope needs to fold into a compact package.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/nasawebbtelescope/51404134793/in/album-72157629134274763/">NASA/Chris Gunn</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Some alignment required</h2>
<p>The Webb team continued to rehearse and practice until the launch date, but our work is far from done now. </p>
<p>[<em>Understand new developments in science, health and technology, each week.</em> <a href="https://members.theconversation.com/newsletters/?nl=science&source=inline-science-understand">Subscribe to The Conversation’s science newsletter</a>.]</p>
<p>We need to wait 35 days after launch for the parts to cool before beginning alignment. After the mirror unfolds, NIRCam will snap sequences of high-resolution images of the individual mirror segments. The telescope team will analyze the images and tell motors to adjust the segments in steps measured in billionths of a meter. Once the motors move the mirrors into position, we will confirm that telescope alignment is perfect. This task is so mission critical that there are two identical copies of NIRCam on board – if one fails, the other can take over the alignment job. </p>
<p>This alignment and checkout process should take six months. When finished, Webb will begin collecting data. After 20 years of work, astronomers will at last have a telescope able to peer into the farthest, most distant reaches of the universe.</p>
<p><em>This story was updated with the launch.</em></p><img src="https://counter.theconversation.com/content/167516/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Marcia Rieke receives funding from NASA. Her endowed chair is paritially funded by the Heisings-Simon Foundation.</span></em></p>The largest orbital telescope ever made will allow astronomers to study the atmospheres of alien planets, learn about how stars form in the Milky Way and peer into the farthest reaches of the universe.Marcia Rieke, Regents Professor of Astronomy, University of ArizonaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1663532021-08-23T15:10:45Z2021-08-23T15:10:45ZAnalysis of 2 000 galaxies using the MeerKat radio telescope reveals fresh insights<figure><img src="https://images.theconversation.com/files/416726/original/file-20210818-21-1ngevx2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">MeerKAT, the precursor to the massive Square Kilometre Array, allows astronomers to gather huge amounts of data about galaxies.</span> <span class="attribution"><span class="source">Photo by Jaco Marais/Foto24/Gallo Images/Getty Images</span></span></figcaption></figure><p>Galaxies – massive collections of gas, dust, and billions of stars and their solar systems – are a fundamental component of our Universe. Understanding how they have formed and evolved over cosmic eras remains one of the greatest challenges of modern astronomy. </p>
<p>There are a few reasons for this. First, the number of galaxies: astronomers <a href="https://singularityhub.com/2021/01/15/how-many-galaxies-are-in-the-universe-a-new-answer-emerges-from-the-darkest-sky-ever-observed/">have estimated</a> that there are roughly 200 billion galaxies in our Universe. Second, the sheer size and age of these galaxies. Their ages range from 100 million to 10 billion years and the size ranges from roughly 3,000 to 300,000 light years. One light year is 9.46 x 10¹² km – clearly, then, galaxies are huge and ancient.</p>
<p>However, galaxies aren’t totally mysterious. Technology is allowing astronomers to study and analyse them in far more detail than was previously possible. Our <a href="https://academic.oup.com/mnras/advance-article-abstract/doi/10.1093/mnras/stab2290/6346552?redirectedFrom=fulltext">new study</a> used observations from the powerful MeerKAT radio telescope array, located in South Africa, to analyse more than 2,000 galaxies. MeerKAT is the most sensitive radio telescope in the southern hemisphere until the <a href="https://www.skatelescope.org/">Square Kilometre Array</a> (SKA, which will be the world’s largest radio telescope) is completed. </p>
<p>Our findings suggest that, within the galaxies we analysed, their course of evolution is likely accompanied by cosmic ray electrons losing energy with time. The energy does not – and cannot – simply vanish. Instead, as the electrons slow down, their energy is converted into that of the electromagnetic emissions. These emissions, after escaping the confines of the galaxy and traversing the cosmic distances, are among the telltale signals picked up by the MeerKAT.</p>
<p>These findings help us better understand the nature of these galaxies, and furthermore, the formation and evolution of galaxies in general – including our home galaxy, the Milky Way, which may be undergoing a similar process at the moment. This isn’t a process to worry about; it’s just something scientists want to understand better.</p>
<h2>Combining the data</h2>
<p>Our study was what’s called a statistical analysis. Different astrophysical phenomena create electromagnetic waves in different wavelengths, including radio, visible light, infrared, ultraviolet, and x-rays. It is therefore important to be able to combine different observations across a broad range of spectra. That’s what a statistical analysis allows.</p>
<p>We selected 2,094 galaxies that are active in forming stars, which means they are energetic and young – in cosmic time-scales. This is an ideal sample to study the way that galaxies grow up and the key features that affect their formation and evolution. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/416710/original/file-20210818-23-g3x5g8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/416710/original/file-20210818-23-g3x5g8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=530&fit=crop&dpr=1 600w, https://images.theconversation.com/files/416710/original/file-20210818-23-g3x5g8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=530&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/416710/original/file-20210818-23-g3x5g8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=530&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/416710/original/file-20210818-23-g3x5g8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=666&fit=crop&dpr=1 754w, https://images.theconversation.com/files/416710/original/file-20210818-23-g3x5g8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=666&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/416710/original/file-20210818-23-g3x5g8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=666&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Correlation between the mass of the galaxies (X-axis) and the difference of their radio emissions at different radio frequencies (Y-axis). Each symbol represents an individual galaxy. The image of an example galaxy is from NASA/ESA Hubble Space Telescope. T means the time for light to travel from these galaxies to us.</span>
<span class="attribution"><span class="source">Image created by Fangxia An (IDIA/UWC).</span></span>
</figcaption>
</figure>
<p>The distances to these galaxies are so great that light, the fastest messenger in the Universe, takes roughly 1 to 11 billion years to arrive from them. So, the galaxies we observe now reflect how they used to be roughly 1 to 11 billion years ago; they are at different evolutionary stages. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/discovery-of-two-new-giant-radio-galaxies-offers-fresh-insights-into-the-universe-153457">Discovery of two new giant radio galaxies offers fresh insights into the universe</a>
</strong>
</em>
</p>
<hr>
<p>Next, we studied the fundamental physical properties of these distant galaxies by combining the new observations from MeerKAT and the existing observational data from other telescopes. The MeerKAT data were collected over nearly 20 hours as part of the MeerKAT International GHz Tiered Extragalactic Exploration (<a href="http://idia.ac.za/mightee/">MIGHTEE</a>) project. This seeks to observe the deep extragalactic space to explore the cosmic evolution of galaxies. It is one of the MeerKAT’s large survey projects prioritised by the <a href="https://www.sarao.ac.za/about/sarao/">South African Radio Astronomy Observatory</a>.</p>
<h2>Key findings</h2>
<p>By combining the emission of light in visible, infra-red, and radio from these selected 2,094 galaxies, the study measured how massive, how active, and how bright they appear to be at different radio frequencies, as well as some other fundamental physical properties. Then we connected the intensities of radio emission with the measured physical properties of these galaxies.</p>
<p>The difference between the radio emissions at different radio frequencies was correlated with the mass of the galaxies. On average, the most massive galaxies show the largest difference of radio emission intensity at different radio frequencies. On average, we find that the more massive a galaxy is, the larger such a difference tends to be. </p>
<p>Further quantitative analysis shows that this statistical trend is consistent with the radio emission from cosmic ray electrons that are gradually slowing down – a process that accompanies these galaxies throughout different stages of evolution.</p><img src="https://counter.theconversation.com/content/166353/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Fangxia An is affiliated with Inter-University Institute for Data Intensive Astronomy, and Department of Physics and Astronomy, University of the Western Cape. </span></em></p>Technology is allowing astronomers to study and analyse galaxies in far more detail than was previously possible.Fangxia An, Postdoctoral researcher, Inter-University Institute for Data Intensive AstronomyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1647092021-07-20T02:49:51Z2021-07-20T02:49:51ZA new image shows jets of plasma shooting out of a supermassive black hole<figure><img src="https://images.theconversation.com/files/412048/original/file-20210720-19-ragc5m.jpg?ixlib=rb-1.1.0&rect=4%2C36%2C278%2C278&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Event Horizon Telescope project/Nature Astronomy</span></span></figcaption></figure><p>In 2019, when astronomers captured the first image of a <a href="https://iopscience.iop.org/article/10.3847/2041-8213/ab1141">black hole’s shadow</a> — a bright orange doughnut-shaped halo created by the black hole’s intense gravity bending light around it — it was rightly <a href="https://www.sciencemag.org/news/2019/04/black-hole">hailed as a breakthrough</a>. </p>
<p>Now, I have joined the <a href="https://eventhorizontelescope.org/">Event Horizon Telescope</a> team in following up on their earlier achievement, by creating a new image showing jets of plasma being ejected from the core of a different supermassive black hole, at the centre of the galaxy Centaurus A.</p>
<p>Centaurus A’s black hole is about 120 times less massive than that of M87, the galaxy where the black hole halo was spotted (and which also has its own set of plasma jets). So no black hole shadow was expected or seen in Centaurus A’s case.</p>
<p>But the results, <a href="https://www.nature.com/articles/s41550-021-01417-w">published in Nature Astronomy</a>, nevertheless provide another fascinating insight into the huge black holes that lurk at the centre of many galaxies.</p>
<p>Centaurus A is so-named because it is the brightest (hence “A”) object in the constellation Centaurus, in the southern skies. Centaurus A appears as one of the largest radio galaxies in our skies, because of its relative closeness, at 15 million light years from Earth.</p>
<p>In the visible light spectrum, this galaxy is characterised by a dark “dust lane” that blocks our view of its centre. But radio waves are unaffected by this material, so radioastronomers can study its centre in detail. </p>
<p>Centaurus A, like other “active” galaxies, has a supermassive black hole at its centre, which is fed by material falling in towards it. Much of that material ends up falling into, or orbiting around, the black hole. But some of it – through a process not yet understood – is shot out in a pair of diametrically opposed “jets”.</p>
<p>These plasma jets are one of the most mysterious and energetic features of galaxies. They travel at speeds close to the speed of light, and so the effects of Einstein’s theory of relativity become important. </p>
<p>One prediction is that the jet travelling towards us will appear brighter, while the opposing jet, travelling away from us, will appear fainter.</p>
<p>In fact, detailed studies of most active galaxies only reveal a one-sided jet, with the counter-jet too faint to observe.</p>
<p>Centaurus A is one of the few examples for which both the jet and counter-jet have <a href="https://ui.adsabs.harvard.edu/abs/1996ApJ...466L..63J/abstract">previously been seen</a>. Observations with a network of telescopes, including CSIRO’s 64-metre Parkes telescope and Australia Telescope Compact Array, had provided the most detailed images before now. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/a-brain-transplant-for-one-of-australias-top-telescopes-129138">A brain transplant for one of Australia's top telescopes</a>
</strong>
</em>
</p>
<hr>
<p>Our team used an international network of seven telescopes spanning North and South America and Antarctica. (Australia sadly doesn’t have the high-altitude observation sites necessary to make this kind of observation.)</p>
<p>The telescopes imaged the black hole’s jets in 16 times more detail than previous images. This revealed two things: first, and slightly surprisingly, nothing is seen in the vicinity of the black hole itself; and second, and even more intriguingly, only the outer edges of the jets seem to emit radiation. </p>
<p>While this “edge-brightening” has been seen for several other nearby active galaxies, this is the first time it has been seen in Centaurus A, and seen so clearly.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/411853/original/file-20210719-27-11057h.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Radioastronomy images of black hole plasma jets" src="https://images.theconversation.com/files/411853/original/file-20210719-27-11057h.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/411853/original/file-20210719-27-11057h.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=250&fit=crop&dpr=1 600w, https://images.theconversation.com/files/411853/original/file-20210719-27-11057h.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=250&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/411853/original/file-20210719-27-11057h.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=250&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/411853/original/file-20210719-27-11057h.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=314&fit=crop&dpr=1 754w, https://images.theconversation.com/files/411853/original/file-20210719-27-11057h.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=314&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/411853/original/file-20210719-27-11057h.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=314&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Left: the previous best image of the Centaurus A black hole’s plasma jets; middle: the new image; right: the larger plasma jets from M87’s black hole.</span>
<span class="attribution"><span class="source">Nature Astronomy</span></span>
</figcaption>
</figure>
<p>The edge of the jet may be brightened by the interaction of the jet plasma with the gas and dust in the galaxy. The narrowness of the jets also hints that strong magnetic fields may be coiled around the jet, and these may also lead to brighter edges and create an invisible “spine” to the jet. </p>
<p>The overall geometry and properties of the jet bear a striking resemblance to those of the jet in M87, as well as to jets launched by smaller black holes (tens of solar masses rather than millions or billions) in our own galaxy, the Milky Way. This supports the idea that the same processes happen in both supermassive black holes and their lighter counterparts, suggesting supermassive black holes are simply a scaled-up version of smaller ones, without requiring any new (or additional) physical mechanisms to be invoked.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/cosmic-jets-whats-shooting-out-of-black-holes-20155">Cosmic jets: what's shooting out of black holes?</a>
</strong>
</em>
</p>
<hr>
<p>As to why we saw nothing in the vicinity of the supermassive black hole itself, it is possible our line of sight is blocked by dense matter falling towards the black hole. We might be able to see more by increasing our observing frequency into the terahertz range, but that is a huge technical challenge.</p>
<p>COVID restrictions resulted in our 2020 observing campaign being abandoned, however the Event Horizon Telescope array was back in operation for a campaign in April this year, with further observations of M87 and Centaurus A on its list of targets. </p>
<p>Another source that has already been observed is the supermassive black hole at the centre of the Milky Way. Much closer than those of Centaurus A (15 million light years) or M87 (55 million light years), it is “only” 25,000 light years away, but it is also much less massive — roughly five million times the mass of our Sun. </p>
<p>While we believe this black hole has been <a href="https://theconversation.com/a-dormant-volcano-the-black-hole-at-the-heart-of-our-galaxy-is-more-explosive-than-we-thought-124696">active in the distant past</a>, recent observations have not revealed any bright jets emerging from the centre of our galaxy, suggesting it is not currently as active, but could potentially become active again in the future. It will be interesting to see what our forthcoming observations reveal.</p><img src="https://counter.theconversation.com/content/164709/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Phil Edwards does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Astronomers have taken a close-up look at the jets of plasma streaking away from a supermassive black hole - one of the strangest and most energetic features of galaxies.Phil Edwards, Program Director, Australia Telescope National Facility Science, CSIROLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1640622021-07-19T12:06:44Z2021-07-19T12:06:44ZAre there any planets outside of our solar system?<figure><img src="https://images.theconversation.com/files/410219/original/file-20210707-25-2zom23.jpg?ixlib=rb-1.1.0&rect=31%2C15%2C5161%2C2903&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Artist illustration of an exoplanet.
</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/beautiful-exoplanet-with-exo-moons-orbiting-an-royalty-free-image/873145010?adppopup=true">dottedhippo/iStock via Getty Images</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
<hr>
<blockquote>
<p><strong>Are there any planets outside of our solar system? - Eli W., age 8, Baton Rouge, Louisiana</strong></p>
</blockquote>
<hr>
<p>This is a question that human beings have wondered about for thousands of years. </p>
<p>Here’s how the ancient Greek mathematician <a href="https://en.wikipedia.org/wiki/Metrodorus_of_Chios">Metrodorus</a> (400-350 B.C.) put it: A universe where Earth is “the only world,” he said, is about as believable as a “large field containing a single stalk.” </p>
<p>About 2,000 years later, in the 16th century, the Italian philosopher <a href="https://www.britannica.com/biography/Giordano-Bruno">Giordano Bruno</a> suggested something similar. </p>
<p>“Countless suns and countless earths” existed elsewhere, he said, all rotating “round their suns in exactly the same way as the planets of our system.” </p>
<p>Scientists now know that both Metrodorus and Bruno were essentially correct. Today, <a href="https://scholar.google.com/citations?hl=en&user=VRJuiHUAAAAJ">astronomers like me</a> are still exploring this question, using new tools. </p>
<figure class="align-center ">
<img alt="An exoplanet orbiting a red dwarf star." src="https://images.theconversation.com/files/410231/original/file-20210707-6685-1pr3hko.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/410231/original/file-20210707-6685-1pr3hko.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=350&fit=crop&dpr=1 600w, https://images.theconversation.com/files/410231/original/file-20210707-6685-1pr3hko.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=350&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/410231/original/file-20210707-6685-1pr3hko.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=350&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/410231/original/file-20210707-6685-1pr3hko.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=439&fit=crop&dpr=1 754w, https://images.theconversation.com/files/410231/original/file-20210707-6685-1pr3hko.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=439&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/410231/original/file-20210707-6685-1pr3hko.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=439&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">An exoplanet orbiting a red dwarf, a star that is dimmer than our Sun and about half the size.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/artwork-of-gliese-887-b-and-c-royalty-free-illustration/1271698835">Mark Garlick/Science Photo Library via Getty Images</a></span>
</figcaption>
</figure>
<h2>The exoplanets</h2>
<p>There is now evidence that demonstrates the existence of “exoplanets” – that is, planets orbiting stars other than our Sun. </p>
<p>That evidence is based on the discoveries made by the <a href="https://kidsdiscover.com/spotlight/kepler/">Kepler space telescope</a>, launched by NASA in 2009.</p>
<p>For four years, the telescope stared continuously at a single region of space within the <a href="https://kids.kiddle.co/Cygnus_(constellation)">constellation Cygnus</a>.</p>
<p>Looking from Earth, it’s an area that takes up less than 1% of your view of the sky. </p>
<figure class="align-center ">
<img alt="An illustration shows the Kepler telescope in space, next to a star and its planet." src="https://images.theconversation.com/files/410236/original/file-20210707-25-1fxhfsx.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/410236/original/file-20210707-25-1fxhfsx.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=350&fit=crop&dpr=1 600w, https://images.theconversation.com/files/410236/original/file-20210707-25-1fxhfsx.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=350&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/410236/original/file-20210707-25-1fxhfsx.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=350&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/410236/original/file-20210707-25-1fxhfsx.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=440&fit=crop&dpr=1 754w, https://images.theconversation.com/files/410236/original/file-20210707-25-1fxhfsx.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=440&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/410236/original/file-20210707-25-1fxhfsx.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=440&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Artist illustration of NASA’s Kepler space telescope.</span>
<span class="attribution"><a class="source" href="https://exoplanets.nasa.gov/news/1526/latest-on-the-kepler-spacecraft/">NASA Images</a></span>
</figcaption>
</figure>
<h2>How the telescope worked</h2>
<p>Kepler had 42 cameras on board, similar to the kind of smartphone camera that you use to take pictures. In that one region, the telescope detected more than 150,000 stars. </p>
<p>About every half-hour it observed the amount of light radiating from each star. Back here on Earth, a team of Kepler scientists analyzed the data.</p>
<p>For most stars, the amount of light stayed pretty much the same. </p>
<p>But for about 3,000 stars, the amount of light repeatedly decreased, by small amounts and for several hours. These drops in brightness happened at regular intervals, like clockwork. </p>
<p>The drops, astronomers concluded, were caused by a planet orbiting its star, periodically blocking some of the light that Kepler’s cameras would otherwise detect. </p>
<p>This event – when a planet passes between a star and its observer – is known as a <a href="https://exoplanets.nasa.gov/faq/31/whats-a-transit/">transit</a>.</p>
<p>And that means that in that one speck of space the Kepler telescope found 3,000 planets.</p>
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<figcaption><span class="caption">NASA Video: Animation of a exoplanet transiting its star.</span></figcaption>
</figure>
<h2>That’s only the beginning</h2>
<p>Although 3,000 planets sounds like a lot, it’s certain many others within that area remain undetected. </p>
<p>That’s because their orbits never blocked the light as seen by Kepler. After all, planetary orbits aren’t all the same; they’re randomly oriented. </p>
<p>But because of the number of transits observed by Kepler, and astronomers’ knowledge of geometry, we can make a good guess on the total number of exoplanets out there.</p>
<p>And after making those calculations, scientists now think, on average, <a href="https://www.popsci.com/science/article/2012-01/new-exoplanet-analysis-determines-planets-are-more-common-stars-milky-way/">that every star has at least one planet</a>. </p>
<p>This discovery has revolutionized astronomy and our view of the universe. </p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/4IXYp9Fse44?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">NASA Video: Weird and Wondrous Worlds.</span></figcaption>
</figure>
<h2>100 billion stars, 100 billion planets</h2>
<p>For instance, our Milky Way galaxy has at least 100 billion stars; that means it has at least 100 billion planets too.</p>
<p>But remember: The universe holds up to 2 trillion galaxies. That’s 2,000,000,000,000! And each galaxy contains tens or even hundreds of billions of stars. </p>
<p>So the number of planets in the universe is truly astronomical, roughly equivalent to the <a href="https://www.universetoday.com/106725/are-there-more-grains-of-sand-than-stars/">number of grains of dry sand</a> on every beach on Earth. </p>
<p>Some of those planets are gas giants, like <a href="https://spaceplace.nasa.gov/all-about-jupiter/en/">Jupiter</a> in our solar system. Others are boiling hot, like <a href="https://spaceplace.nasa.gov/all-about-venus/en/">Venus</a>. Others may be <a href="https://www.nasa.gov/specials/ocean-worlds/">water worlds</a> or <a href="https://spaceplace.nasa.gov/ice-on-other-planets/en/">ice planets</a>. And some are Earth-like.</p>
<p>In fact, the Kepler team calculated the abundance of Earth-like planets in the “habitable zone,” a sector of space around each star where a world might have moderate temperatures and liquid water. </p>
<p>They found approximately <a href="https://www.nasa.gov/feature/ames/kepler-occurrence-rate">50% of Sun-like stars in the Milky Way</a> host an Earth-like planet in the habitable zone. </p>
<p>That adds up to <a href="https://www.space.com/habitable-planets-common-sunlike-stars-milky-way">billions of potentially habitable worlds</a> just in our galaxy.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/J04YN9azln8?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">NASA/JPL-Caltech Video: What is the “Habitable Zone”?</span></figcaption>
</figure>
<h2>Could life exist elsewhere?</h2>
<p>Although scientists haven’t found proof yet, many – <a href="https://seti.ucla.edu/jlm/">including me</a> – now think it’s unlikely that Earth is the only planet where life evolved. That would be as surprising as a large field containing a single stalk.</p>
<p>When will humans detect life elsewhere? Will it be intelligent life? Will people ever receive a message from another civilization?</p>
<p>Today, hundreds of scientists around the world are trying to answer those questions.</p>
<hr>
<p><em>Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>.
Please tell us your name, age and the city where you live.</em></p>
<p><em>And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.</em></p><img src="https://counter.theconversation.com/content/164062/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jean-Luc Margot receives funding from the National Aeronautics and Space Administration, the National Science Foundation, and philanthropists.</span></em></p>Billions of galaxies are in the universe, with billions of stars in every galaxy. Could billions of planets be out there too?Jean-Luc Margot, Professor of Earth, Planetary, and Space Sciences, University of California, Los AngelesLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1614192021-05-24T21:17:34Z2021-05-24T21:17:34ZStellar secrets of a distant galaxy suggest our Milky Way isn’t so special after all<figure><img src="https://images.theconversation.com/files/402309/original/file-20210524-21-g66d8r.jpg?ixlib=rb-1.1.0&rect=4%2C0%2C3291%2C2000&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption"></span> <span class="attribution"><span class="license">Author provided</span></span></figcaption></figure><p>It’s no surprise the Milky Way is the most-studied galaxy in the universe, given it’s where we live.</p>
<p>But studying just one galaxy can only tell us so much about the complex processes by which galaxies form and evolve.</p>
<p>One crucial question that can’t be solved without looking farther afield is whether the Milky Way is a run-of-the-mill galaxy, or whether it’s unusual or even unique.</p>
<p>Our research, <a href="https://iopscience.iop.org/article/10.3847/2041-8213/abfc57">published today in The Astrophysical Journal Letters</a>, suggests the former is true. Key details of our galaxy’s structure are shared by other nearby galaxies, suggesting our home isn’t all that special. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/402280/original/file-20210524-17-1qcp7sz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/402280/original/file-20210524-17-1qcp7sz.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=300&fit=crop&dpr=1 600w, https://images.theconversation.com/files/402280/original/file-20210524-17-1qcp7sz.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=300&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/402280/original/file-20210524-17-1qcp7sz.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=300&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/402280/original/file-20210524-17-1qcp7sz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=377&fit=crop&dpr=1 754w, https://images.theconversation.com/files/402280/original/file-20210524-17-1qcp7sz.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=377&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/402280/original/file-20210524-17-1qcp7sz.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=377&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">An all-sky map of the Milky Way from ESA’s Gaia satellite.</span>
</figcaption>
</figure>
<p>At first glance, there’s no reason to suspect our galaxy is remarkable anyway. Among the billions of galaxies in the observable universe, ours is not the largest, oldest or most massive. It looks pretty much like all other spiral galaxies, which is the most common type of galaxy.</p>
<p>But when we look in detail at the Milky Way’s structure and chemistry, it starts to stand out.</p>
<p>From side-on (where it’s impossible to make out the spiral arms), it looks like a pancake with a peach in the middle. Astronomers have known that for at least a century.</p>
<p>However, that simple picture changed in 1983, when researchers using Australian telescopes <a href="https://academic.oup.com/mnras/article/202/4/1025/1008233">discovered</a> an ancient “thick disk” component in the Milky Way. This faint structure is invisible to the naked eye, unlike the dominant thin disk (the pancake-shaped part), which is plainly visible on a clear night as a streak of stars across the sky. </p>
<p>The thin disk, where our Sun resides, is about 1,000 light-years thick and about 100,000 light-years in diameter, and runs through the middle of the thick disk, in the same plane. The thick disk, aptly enough, is much thicker, being a few thousand light-years thick, but is much less densely populated with stars.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/under-the-milky-way-what-a-new-map-reveals-about-our-galaxy-67273">Under the Milky Way: what a new map reveals about our galaxy</a>
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<p>One <a href="https://ui.adsabs.harvard.edu/abs/2013A%26A...560A.109H/abstract">interesting recent discovery</a> is that the thick and thin disks contain very different kinds of stars. Stars in the thin disk tend to have a high proportion of heavy elements such as iron (“metals”, in astronomy parlance) and relatively small amounts of the “alpha elements” (carbon, oxygen, magnesium, silicon and a few others). Thick disk stars, meanwhile, have about 100 times less metals, but significantly more of the alpha elements.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/cuKXQJgkeYg?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Artist’s impression of the Milky Way.</span></figcaption>
</figure>
<p>This double-disk structure, with its very distinct populations of stars, is very tricky to replicate in computer simulations. For a long time, computer models with the same structure could only be created in a specific scenario involving a medium-sized galaxy colliding with our own, roughly nine billion years ago. Simulations suggested this process was incredibly rare: only one in 20 galaxies superficially similar to the Milky Way experienced a collision that resulted in <a href="https://ui.adsabs.harvard.edu/abs/2020MNRAS.497.4311E/abstract">distinct thick and thin disks</a>.</p>
<p>If this scenario were correct, galaxies like the Milky Way should be as rare as hen’s teeth.</p>
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<figcaption><span class="caption">An example of spectral imaging with the MUSE instrument.</span></figcaption>
</figure>
<p>Our research set out to test this clear prediction. We studied a handful of galaxies broadly similar to the Milky Way, using the Multi Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope at the <a href="https://www.eso.org/public/teles-instr/paranal-observatory/vlt/">European Southern Observatory</a> in Chile. </p>
<p>Spectroscopy – splitting the light from a galaxy into many different colours – lets us determine the chemical composition of its stars. What makes MUSE an extremely powerful instrument is that we get 90,000 spectra in a single observation, transforming each location of the galaxy into a spectrum.</p>
<p>One particular galaxy — UGC10738, which is roughly 320 million light-years away – stood out because of its side-on orientation, which allowed us to separate out the thin and thick disk stars and then compare them. </p>
<p>We found that the chemical compositions of stars in UGC 10738 are extremely similar to those in the Milky Way. We found metal-rich, magnesium-poor stars concentrated in a thin disk along the galaxy’s centre, with a distinct group of metal-poor, magnesium-rich stars above and below this, in the thick disk region. </p>
<p>That distant galaxy is remarkably similar to our own. Which in turn means there’s probably nothing that remarkable about the Milky Way after all.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/402284/original/file-20210524-15-1y9mmif.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/402284/original/file-20210524-15-1y9mmif.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=304&fit=crop&dpr=1 600w, https://images.theconversation.com/files/402284/original/file-20210524-15-1y9mmif.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=304&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/402284/original/file-20210524-15-1y9mmif.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=304&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/402284/original/file-20210524-15-1y9mmif.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=382&fit=crop&dpr=1 754w, https://images.theconversation.com/files/402284/original/file-20210524-15-1y9mmif.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=382&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/402284/original/file-20210524-15-1y9mmif.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=382&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Milky Way over the Very Large Telescope at ESO’s Paranal Observatory.</span>
<span class="attribution"><span class="source">A. Russell/ESO</span></span>
</figcaption>
</figure>
<p>Our discovery has several implications. First, it suggests the disk features in the Milky Way might be the result of a standard formation path that all galaxies follow. This is backed up by the <a href="https://www.aanda.org/articles/aa/full_html/2019/05/aa35154-19/aa35154-19.html">identification of similar structures</a> in non-Milky-Way-like galaxies.</p>
<p>Second, the fact that our galaxy is relatively normal is extremely exciting. It implies the Milky Way can act as a blueprint or template for galaxy formation.</p>
<p>This means our home galaxy (which is obviously the easiest for us to study) could hold the key to unlocking the cosmic history of the entire universe.</p>
<p>Finally, and being a little speculative here, the Milky Way is the only galaxy that we know contains life. New research has suggested galactic-scale events may have played a <a href="https://www.nature.com/articles/s41550-020-1097-0">crucial role in the formation of our Solar system</a>. The recent explosion of exoplanet discoveries has shown that systems like it are common throughout the galaxy, suggesting life could find many possible homes within it. </p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/from-pancakes-to-soccer-balls-new-study-shows-how-galaxies-change-shape-as-they-age-95379">From pancakes to soccer balls, new study shows how galaxies change shape as they age</a>
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<p>Now we know the Milky Way’s history was likely similar to many billions of other galaxies, it seems increasingly likely they too might make good homes for life.</p>
<p>Ultimately, whatever future research teaches us, the Milky Way will remain our home. And that makes it special – even though our research suggests that in another sense, it’s not special at all.</p><img src="https://counter.theconversation.com/content/161419/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nicholas Scott works for the University of Sydney and is funded by an Australian Research Council Discovery Early Career Research Award DE190100375. Parts of this research were conducted by the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), through project number CE170100013.</span></em></p><p class="fine-print"><em><span>Jesse van de Sande works for the University of Sydney and is funded by an Australian Research Council Discovery Early Career Research Award DE200100461. Parts of this research were conducted by the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), through project number CE170100013.</span></em></p>A galaxy 320 million light-years away has a surprisingly similar structure to the Milky Way, suggesting our galaxy isn’t as unique as it once seemed to astronomers.Nicholas Scott, Postdoctoral Research Fellow in Astronomy, University of SydneyJesse van de Sande, ARC DECRA Fellow in Astronomy, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1536502021-02-07T19:05:26Z2021-02-07T19:05:26Z5 twinkling galaxies help us uncover the mystery of the Milky Way’s missing matter<figure><img src="https://images.theconversation.com/files/382678/original/file-20210205-14-1cjaiyy.jpg?ixlib=rb-1.1.0&rect=57%2C38%2C6332%2C3554&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption"></span> <span class="attribution"><span class="license">Author provided</span></span></figcaption></figure><p>We’ve all looked up at night and admired the brightly shining stars. Beyond making a gorgeous spectacle, measuring that light helps us learn about matter in our galaxy, the Milky Way.</p>
<p>When astronomers add up all the ordinary matter detectable around us (such as in galaxies, stars and planets), they find only half the amount expected to exist, based on predictions. This normal matter is “<a href="https://www.space.com/20930-dark-matter.html">baryonic</a>”, which means it’s made up of baryon particles such as protons and neutrons.</p>
<p>But about half of this matter in our galaxy is too dark to be detected by even the most powerful telescopes. It takes the form of cold, dark clumps of gas. In this dark gas is the Milky Way’s “missing” baryonic matter. </p>
<p>In a <a href="https://academic.oup.com/mnras/advance-article-abstract/doi/10.1093/mnras/stab139/6105310">paper</a> published in the Monthly Notices of the Royal Astronomical Society, we detail the discovery of five twinkling far-away galaxies that point to the presence of an unusually shaped gas cloud in the Milky Way. We think this cloud may be linked to the missing matter.</p>
<h2>Finding what we can’t see</h2>
<p>Stars twinkle because of turbulence in our atmosphere. When their light reaches Earth, it gets bent as it bounces through different layers of the atmosphere.</p>
<p>Rarely, galaxies can twinkle too, due to the turbulence of gas in the Milky Way. We see this twinkling because of the luminous cores of distant galaxies named “quasars”.</p>
<p>Astronomers can use quasars a bit like backlights, to reveal the presence of clumps of gas around us that would otherwise be impossible to see. The challenge, however, is that it is very rare to catch quasars twinkling.</p>
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<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-do-stars-twinkle-81188">Curious Kids: Why do stars twinkle?</a>
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<p>This is where the <a href="https://theconversation.com/the-australian-square-kilometre-array-pathfinder-finally-hits-the-big-data-highway-71217">Australian Square Kilometre Array Pathfinder</a> (ASKAP) comes in. This highly sensitive telescope can view an area about the size of the Southern Cross and detect tens of thousands of distant galaxies, including quasars, in a single observation. </p>
<p>Using ASKAP, we looked at the same patch of sky seven times. Of the 30,000 galaxies we could see, six were twinkling strongly. Surprisingly, five of these were arranged in a long, thin straight line.</p>
<p>Analysis showed we’d captured an invisible clump of gas between us and the galaxies. As light from the galaxies passed through the gas cloud, they appeared to twinkle. </p>
<iframe src="https://giphy.com/embed/IbzBKUczcgumPpSq1Z" width="100%" height="360" frameborder="0" class="" allow="" fullscreen=""></iframe>
<p> At the centre is one of the strongly twinkling galaxies. The colours represent brightness, as it fluctuates between shining brightly (red) and more faintly (blue). </p>
<h2>A clump of gas ten light years away</h2>
<p>The cloud of gas we detected was inside the Milky Way, about ten light years away from Earth. For reference, one light year is 9.7 trillion kilometres. </p>
<p>That means light from those twinkling galaxies travelled billions of light years towards Earth, only to be disrupted by the cloud during the last ten years of its journey. </p>
<p>By observing the sky positions of not just the five twinkling galaxies, but also tens of thousands of non-twinkling ones, we were able to draw a boundary around the gas cloud.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/380428/original/file-20210125-19-12u4kcg.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/380428/original/file-20210125-19-12u4kcg.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=476&fit=crop&dpr=1 600w, https://images.theconversation.com/files/380428/original/file-20210125-19-12u4kcg.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=476&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/380428/original/file-20210125-19-12u4kcg.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=476&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/380428/original/file-20210125-19-12u4kcg.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=599&fit=crop&dpr=1 754w, https://images.theconversation.com/files/380428/original/file-20210125-19-12u4kcg.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=599&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/380428/original/file-20210125-19-12u4kcg.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=599&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">We were intrigued by the sky positions of the twinkling galaxies in our ASKAP observations. Each black dot above represents a brightly-shining, distant object.</span>
<span class="attribution"><span class="source">Yuanming Wang</span></span>
</figcaption>
</figure>
<p>We found it was very straight, the same length as four Moons side-by-side, and only two “<a href="https://earthsky.org/astronomy-essentials/sky-measurements-degrees-arc-minutes-arc-seconds">arcminutes</a>” in width. This is so thin it’s the equivalent of looking at a strand of hair held at arm’s length. </p>
<p>This is the first time astronomers have been able to calculate the geometry and physical properties of a gas cloud in this way. But where did it come from? And what gave it such an unusual shape?</p>
<h2>It’s freezing out there</h2>
<p>Astronomers have predicted that when a star passes too close to a black hole, the extreme forces from the black hole will pull it apart, resulting in a long, thin gas stream. </p>
<p>But there are no massive black holes near that cloud of gas — the <a href="https://www.bbc.com/news/science-environment-52560812">closest one we know about</a> is more than 1,000 light years from Earth.</p>
<p>So we propose another theory: that a hydrogen “snow cloud” was disrupted and stretched out by gravitational forces from a nearby star, turning into a long thin gas cloud. </p>
<p>Snow clouds have only been studied as theoretical possibilities and are almost impossible to detect. But they would be so cold that droplets of hydrogen gas within them could freeze solid. </p>
<p>Some astronomers believe snow clouds make up part of the missing matter in the Milky Way.</p>
<p>It’s incredibly exciting for us to have measured an invisible clump of gas in such detail, using the ASKAP telescope. In the future we plan to repeat our experiment on a much larger scale and hopefully create a “cloud map” of the Milky Way. </p>
<p>We’ll then be able to work out how many other gas clouds are out there, how they’re distributed and what role they might have played in the evolution of the Milky Way.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/half-the-matter-in-the-universe-was-missing-we-found-it-hiding-in-the-cosmos-138569">Half the matter in the universe was missing – we found it hiding in the cosmos</a>
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<img src="https://counter.theconversation.com/content/153650/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Yuanming Wang receives support from China Scholarship Council, and as a Graduate Student with the University of Sydney and CSIRO Astronomy and Space Science.</span></em></p><p class="fine-print"><em><span>Tara Murphy works for the University of Sydney. She receives funding from the Australian Research Council and is an Associate Investigator in the OzGrav Centre of Excellence for Gravitational Wave Discovery.</span></em></p>Thanks to the discovery of five twinkling galaxies in a rare alignment, astronomers have been able to calculate — for the first time — the properties and geometry of an invisible gas cloud in space.Yuanming Wang, PhD student, University of SydneyTara Murphy, Professor, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1545632021-02-04T07:06:04Z2021-02-04T07:06:04ZThese distant ‘baby’ black holes seem to be misbehaving — and experts are perplexed<figure><img src="https://images.theconversation.com/files/382414/original/file-20210204-14-2u8inb.png?ixlib=rb-1.1.0&rect=0%2C0%2C5476%2C2311&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Dr Natasha Hurley-Walker (Curtin / ICRAR) and The GLEAM Team</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span></figcaption></figure><p>Radio images of the sky have revealed hundreds of “baby” and supermassive black holes in distant galaxies, with the galaxies’ light bouncing around in unexpected ways. </p>
<p>Galaxies are vast cosmic bodies, tens of thousands of light years in size, made up of gas, dust, and stars (like our Sun). </p>
<p>Given their size, you’d expect the amount of light emitted from galaxies would change slowly and steadily, over timescales far beyond a person’s lifetime. </p>
<p>But our research, <a href="https://academic.oup.com/mnras/article-abstract/501/4/6139/6031337?redirectedFrom=fulltext">published</a> in the Monthly Notices of the Royal Astronomical Society, found a surprising population of galaxies whose light changes much more quickly, in just a matter of years.</p>
<h2>What is a radio galaxy?</h2>
<p>Astronomers think there’s a supermassive black hole at the centre of most galaxies. Some of these are “active”, which means they emit a lot of radiation. </p>
<p>Their powerful gravitational fields pull in matter from their surroundings and rip it apart into an orbiting donut of hot plasma called an “accretion disk”.</p>
<p>This disk orbits the black hole at nearly the speed of light. Magnetic fields accelerate high-energy particles from the disk in long, thin streams or “jets” along the rotational axes of the black hole. As they get further from the black hole, these jets blossom into large mushroom-shaped clouds or “lobes”.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/382398/original/file-20210204-18-coa4jt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Radio galaxy with bright yellow core, long thin jets extending in opposite directions and large red lobes" src="https://images.theconversation.com/files/382398/original/file-20210204-18-coa4jt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/382398/original/file-20210204-18-coa4jt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=426&fit=crop&dpr=1 600w, https://images.theconversation.com/files/382398/original/file-20210204-18-coa4jt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=426&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/382398/original/file-20210204-18-coa4jt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=426&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/382398/original/file-20210204-18-coa4jt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=536&fit=crop&dpr=1 754w, https://images.theconversation.com/files/382398/original/file-20210204-18-coa4jt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=536&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/382398/original/file-20210204-18-coa4jt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=536&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The radio galaxy Hercules A has an active supermassive black hole at its centre. Here it is pictured emitting high energy particles in jets expanding out into radio lobes.</span>
<span class="attribution"><span class="source">NASA/ESA/NRAO</span></span>
</figcaption>
</figure>
<p>This entire structure is what makes up a radio galaxy, so called because it gives off a lot of radio-frequency radiation. It can be hundreds, thousands or even millions of light years across and therefore can take aeons to show any dramatic changes.</p>
<p>Astronomers have long questioned why some radio galaxies host enormous lobes, while others remain small and confined. Two theories exist. One is that the jets are held back by dense material around the black hole, often referred to as frustrated lobes. </p>
<p>However, the details around this phenomenon remain unknown. It’s still unclear whether the lobes are only temporarily confined by a small, extremely dense surrounding environment — or if they’re slowly pushing through a larger but less dense environment.</p>
<p>The second theory to explain smaller lobes is the jets are young and have not yet extended to great distances. </p>
<h2>Old ones are red, babies are blue</h2>
<p>Both young and old radio galaxies can be identified by a clever use of modern radio astronomy: looking at their “radio colour”.</p>
<p>We looked at data from the <a href="https://theconversation.com/what-the-universe-looks-like-when-viewed-with-radio-eyes-66381">GaLactic and Extragalactic All Sky MWA (GLEAM) survey</a>, which sees the sky at 20 different radio frequencies, giving astronomers an unparalleled “radio colour” view of the sky. </p>
<p>From the data, baby radio galaxies appear blue, which means they’re brighter at higher radio frequencies. Meanwhile the old and dying radio galaxies appear red and are brighter in the lower radio frequencies.</p>
<p>We identified 554 baby radio galaxies. When we looked at identical data taken a year later, we were surprised to see 123 of these were bouncing around in their brightness, appearing to flicker. This left us with a puzzle. </p>
<p>Something more than one light year in size can’t vary so much in brightness over less than one year without breaking the laws of physics. So, either our galaxies were far smaller than expected, or something else was happening. </p>
<p>Luckily, we had the data we needed to find out.</p>
<p>Past research on the variability of radio galaxies has used either a small number of galaxies, archival data collected from many different telescopes, or was conducted using only a single frequency. </p>
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<strong>
Read more:
<a href="https://theconversation.com/weve-mapped-a-million-previously-undiscovered-galaxies-beyond-the-milky-way-take-the-virtual-tour-here-148442">We've mapped a million previously undiscovered galaxies beyond the Milky Way. Take the virtual tour here.</a>
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<p>For our research, we surveyed more than 21,000 galaxies over one year across multiple radio frequencies. This makes it the first “spectral variability” survey, enabling us to see how galaxies change brightness at different frequencies. </p>
<p>Some of our bouncing baby radio galaxies changed so much over the year we doubt they are babies at all. There’s a chance these compact radio galaxies are actually angsty teens rapidly growing into adults much faster than we expected.</p>
<p>While most of our variable galaxies increased or decreased in brightness by roughly the same amount across all radio colours, some didn’t. Also, 51 galaxies changed in both brightness <em>and</em> colour, which may be a clue as to what causes the variability.</p>
<h2>3 possibilities for what is happening</h2>
<p><strong>1) Twinkling galaxies</strong></p>
<p>As light from stars travels through Earth’s atmosphere, it is distorted. This creates the twinkling effect of stars we see in the night sky, called “scintillation”. The light from the radio galaxies in this survey passed through our Milky Way galaxy to reach our telescopes on Earth. </p>
<p>Thus, the gas and dust within our galaxy could have distorted it the same way, resulting in a twinkling effect. </p>
<p><strong>2) Looking down the barrel</strong></p>
<p>In our three-dimensional Universe, sometimes black holes shoot high energy particles directly towards us on Earth. These radio galaxies are called “blazars”. </p>
<p>Instead of seeing long thin jets and large mushroom-shaped lobes, we see blazars as a very tiny bright dot. They can show extreme variability in short timescales, since any little ejection of matter from the supermassive black hole itself is directed straight towards us. </p>
<p><strong>3) Black hole burps</strong></p>
<p>When the central supermassive black hole “burps” some extra particles they form a clump slowly travelling along the jets. As the clump propagates outwards, we can detect it first in the “radio blue” and then later in the “radio red”.</p>
<p>So we may be detecting giant black hole burps slowly travelling through space. </p>
<h2>Where to now?</h2>
<p>This is the first time we’ve had the technological ability to conduct a large-scale variability survey over multiple radio colours. The results suggest our understanding of the radio sky is lacking and perhaps radio galaxies are more dynamic than we expected. </p>
<figure class="align-center ">
<img alt="Artist's impression of the SKA: on the left multiple dishes scattered around representing SKA_MID and on the right a large collection of antennas representing SKA_LOW." src="https://images.theconversation.com/files/382417/original/file-20210204-18-kxrm5w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/382417/original/file-20210204-18-kxrm5w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=300&fit=crop&dpr=1 600w, https://images.theconversation.com/files/382417/original/file-20210204-18-kxrm5w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=300&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/382417/original/file-20210204-18-kxrm5w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=300&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/382417/original/file-20210204-18-kxrm5w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=377&fit=crop&dpr=1 754w, https://images.theconversation.com/files/382417/original/file-20210204-18-kxrm5w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=377&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/382417/original/file-20210204-18-kxrm5w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=377&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">An artist’s impression of the SKA telescope. On the left is SKA-Mid, fading into SKA-Low on the right.</span>
<span class="attribution"><span class="source">SKAO/ICRAR/SARAO</span></span>
</figcaption>
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<p>As the next generation of telescopes come online, in particular the Square Kilometre Array (SKA), astronomers will build up a dynamic picture of the sky over many years.</p>
<p>In the meantime, it’s worth watching these weirdly behaving radio galaxies and keeping a particularly close eye on the bouncing babies, too.</p>
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<strong>
Read more:
<a href="https://theconversation.com/the-worlds-oldest-story-astronomers-say-global-myths-about-seven-sisters-stars-may-reach-back-100-000-years-151568">The world's oldest story? Astronomers say global myths about 'seven sisters' stars may reach back 100,000 years</a>
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<img src="https://counter.theconversation.com/content/154563/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kathryn Ross receives funding from the Australian Research Training Program (RTP), funded by the Australian Government. </span></em></p><p class="fine-print"><em><span>Dr Natasha Hurley-Walker is supported by an Australian Research Council Future Fellowship (project number FT190100231), funded by the Australian Government.</span></em></p>Some of the baby radio galaxies found may not be ‘babies’ at all. Rather, they may be ‘angsty teens’, rapidly growing into adults much faster than researchers had anticipated.Kathryn Ross, PhD Student, Curtin UniversityNatasha Hurley-Walker, Radio Astronomer, Curtin UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1534572021-01-18T13:19:03Z2021-01-18T13:19:03ZDiscovery of two new giant radio galaxies offers fresh insights into the universe<figure><img src="https://images.theconversation.com/files/379206/original/file-20210118-17-1ljd4mt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The two giant radio galaxies found with the MeerKAT telescope. In the background is the sky as seen in optical light. Overlaid in red is the radio light from the enormous radio galaxies, as seen by MeerKAT.</span> <span class="attribution"><span class="source">I. Heywood (Oxford/Rhodes/SARAO)</span></span></figcaption></figure><p>Two giant radio galaxies have been discovered with South Africa’s powerful <a href="https://www.sarao.ac.za/science/meerkat/">MeerKAT telescope</a>, located in the Karoo region, a semi-arid area in the south west of the country. Radio galaxies get their name from the fact that they release huge beams, or ‘jets’, of radio light. These happen through the interaction between charged particles and strong magnetic fields related to supermassive black holes at the galaxies’ hearts.</p>
<p>These giant galaxies are much bigger than most of the others in the Universe and are thought to be quite rare. Although millions of radio galaxies are known to exist, only around 800 giants have been found. This population of galaxies was previously hidden from us by radio telescopes’ limitations. But the MeerKAT has allowed new discoveries because it can detect faint, diffuse light which previous telescopes were unable to do.</p>
<p>Our discovery, <a href="https://academic.oup.com/mnras/article/501/3/3833/6034001">published</a> in the Monthly Notices of the Royal Astronomical Society, gives astronomers further clues about how galaxies have changed and evolved throughout cosmic history. It’s also a way to understand how galaxies may continue to change and evolve – and even to work out how old radio galaxies can get.</p>
<p><audio preload="metadata" controls="controls" data-duration="470" data-image="" data-title="How we discovered two new giant radio galaxies" data-size="7585585" data-source="The Conversation Africa - Pasha" data-source-url="" data-license="CC BY-NC-ND" data-license-url="http://creativecommons.org/licenses/by-nc-nd/4.0/">
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How we discovered two new giant radio galaxies.
<span class="attribution"><span class="source">The Conversation Africa - Pasha</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a><span class="download"><span>7.23 MB</span> <a target="_blank" href="https://cdn.theconversation.com/audio/2111/galaxies-final-version.mp3">(download)</a></span></span>
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<p>The giant radio galaxies were spotted in new radio maps of the sky created by one of the most advanced surveys of distant galaxies. The team working on it has included astronomers from around the world including South Africa, the UK, Italy and Australia. Called the International Gigahertz Tiered Extragalactic Exploration (<a href="http://idia.ac.za/mightee/">MIGHTEE</a>) survey, it involves data collected by South Africa’s impressive MeerKAT radio telescope. MeerKAT consists of 64 antennae and dishes, and started <a href="https://theconversation.com/how-were-probing-the-secrets-of-a-giant-black-hole-at-our-galaxys-centre-108181">collecting science data</a> in early 2018. It will ultimately be incorporated into the <a href="https://www.skatelescope.org/">Square Kilometre Array</a>, an intergovernmental radio telescope project spearheaded by Australia and South Africa.</p>
<p>The galaxies in question are several billion light years away. The discovery of enormous jets and lobes in the MIGHTEE map allowed us to confidently identify the objects as giant radio galaxies.</p>
<p>Their discovery means that a clearer understanding of the evolutionary pathways of galaxies is beginning to emerge. This is tantalising evidence that a large population of faint, very extended giant radio galaxies may exist. This may help us understand how radio galaxies become so huge and what sort of havoc supermassive black holes can wreak on their galaxies. </p>
<h2>What’s new</h2>
<p>Many galaxies have supermassive black holes in their midst. When large amounts of interstellar gas start to orbit and fall in towards the black hole, the black hole becomes ‘active’: huge amounts of energy are released from this region of the galaxy. </p>
<p>In some active galaxies, charged particles interact with the strong magnetic fields near the black hole and release huge beams, or ‘jets’, of radio light. The radio jets of these so-called ‘radio galaxies’ can be many times larger than the galaxy itself and can extend vast distances into intergalactic space. Think of them like jets of water from a whale’s blowhole, a thin column extending into a cloudy plume at the end.</p>
<p>We found these giant radio galaxies in a region of sky that’s about four times the area of the full Moon. Based on what we currently know about the density of giant radio galaxies in the sky, the probability of finding two of them in a region this size is extremely small – only 0.0003%. So, it’s possible that giant radio galaxies – those that emit the beams, or jets of light described above – may actually be more common than we previously thought.</p>
<p>These aren’t the first radio galaxies astronomers have discovered. Many hundreds of thousands have already been identified. But only around 800 have radio jets bigger than 700 kilo-parsecs in size, or around 22 times the size of the Milky Way. These truly enormous systems are called ‘giant radio galaxies’.</p>
<p>Our new discoveries are more than 2 Mega-parsecs across: about 6.5 million light years or about 62 times <a href="https://imagine.gsfc.nasa.gov/features/cosmic/milkyway_info.html">the size of the Milky Way</a>. Yet they are fainter than others of the same size. That’s what makes them harder to see. </p>
<h2>Clues</h2>
<p>We suspect that many more galaxies like these should exist, because of the way we think galaxies should grow and change over their lifetimes. And that’s one question we hope this discovery can help to answer: how old are giant radio galaxies and how did they get so enormous?</p>
<p>Now, telescope technology is making it possible to put these and other theories to the test. MeerKAT is the best of its kind in the world because of the telescope’s unprecedented sensitivity to faint and diffuse radio light. This capability is what made it possible for us to detect the giant radio galaxies. We could see features that haven’t been noticed before: large-scale radio jets coming from the central galaxies, as well as fuzzy cloud-like lobes at the end of the jets.</p>
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<img alt="Two massive satellite dishes are pointed up towards the night sky" src="https://images.theconversation.com/files/379207/original/file-20210118-13-h2vexp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/379207/original/file-20210118-13-h2vexp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=334&fit=crop&dpr=1 600w, https://images.theconversation.com/files/379207/original/file-20210118-13-h2vexp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=334&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/379207/original/file-20210118-13-h2vexp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=334&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/379207/original/file-20210118-13-h2vexp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=420&fit=crop&dpr=1 754w, https://images.theconversation.com/files/379207/original/file-20210118-13-h2vexp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=420&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/379207/original/file-20210118-13-h2vexp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=420&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">South Africa’s MeerKAT telescope.</span>
<span class="attribution"><span class="source">South African Radio Astronomy Observatory (SARAO)</span></span>
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<p>The fact that only very few radio galaxies are so gigantic has always been a bit of a mystery. It is thought that the giants are the oldest radio galaxies, which have existed for long enough (several hundred million years) for their radio jets to grow outwards to these enormous sizes. If this is true, then many more giant radio galaxies should exist than are currently known. And that’s important because radio jets can influence the star formation of their host galaxy. Essentially, they might ‘kill’ their galaxy by blowing out all the gas and preventing the formation of new stars.</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/radio-galaxies-the-mysterious-secretive-beasts-of-the-universe-64381">Radio galaxies: the mysterious, secretive "beasts" of the Universe</a>
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<p>The MIGHTEE survey continues, and we hope to uncover more of these giant galaxies as it progresses. We also expect to find many more with the Square Kilometre Array: construction of this transcontinental telescope is due to start in South Africa and Australia in 2021 and continue until 2027. Science commissioning observations could begin as early as 2023. </p>
<p>The Square Kilometre Array is also expected to reveal larger populations of radio galaxies, revolutionising our understanding of galaxy evolution.</p><img src="https://counter.theconversation.com/content/153457/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jacinta Delhaize receives funding from the South African Radio Astronomy Observatory. </span></em></p>Based on what we currently know about the density of giant radio galaxies in the sky, the probability of finding two of them in this region is extremely small.Jacinta Delhaize, SARAO Postdoctoral Research Fellow, University of Cape TownLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1495882020-11-09T11:41:45Z2020-11-09T11:41:45ZRogue planets: hunting the galaxy’s most mysterious worlds<figure><img src="https://images.theconversation.com/files/367970/original/file-20201106-23-j677s1.jpg?ixlib=rb-1.1.0&rect=92%2C25%2C961%2C551&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">An artist's impression of a gravitational micro-lensing event by a free-floating planet.
</span> <span class="attribution"><a class="source" href="http://www.astrouw.edu.pl/~jskowron/ogle/PR/ffp/">JanSkowron/Astronomical Observatory, University of Warsaw.</a></span></figcaption></figure><p>Most known planets orbit a star. These planets, including Earth, benefit from the star’s warmth and light. And it is the light emitted from these stars which makes it possible for us to see them. But there are also “invisible” planets, hidden from our gaze, which float, abandoned, through the cosmos. These dark, lonely worlds have no star to orbit, no light in which to bask, no warmth to be radiated by. They are the “rogue” planets – and astronomers have just found <a href="https://www.fuw.edu.pl/press-release/news6616.html">a new one</a>, roughly the same size as Earth.</p>
<p>Planets are made from the debris left over after the birth of a star. These planets circle the young star in a thin disc of grains and gas and grow when these small particles stick and pull each other together until they clear their immediate surroundings. Things are chaotic in this world and <a href="https://www.space.com/dirty-collisions-planet-formation.html">collisions</a> between planetary embryos, or proto-planets, are common. Stars tend not to form alone, but in clusters of hundreds or thousands at once, and encounters between their nascent planetary systems cause further havoc.</p>
<p>Young Earth is thought to have been hit by a Mars-sized body, knocking out enough material to <a href="https://theconversation.com/how-the-moon-formed-new-research-133204">form the Moon</a>. But some planets faced a darker future: they were knocked out altogether, destined for a life in the vast coldness of space between the stars. These are the free-floating “rogue planets”.</p>
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<p>When planets are still very young, say just a few million years old (Earth is more than <a href="https://www.nationalgeographic.org/topics/resource-library-age-earth/?q=&page=1&per_page=25">4.5bn years old</a>) they are still warm from their formation and from the energy released by their continued <a href="https://www.tcd.ie/Physics/people/Peter.Gallagher/lectures/PY4A03/pdfs/PY4A03_lecture10n11_ineriors.ppt.pdf">gravitational contraction</a> and radio activity in their cores. Large examples of such young but free-floating planets (think of a baby Jupiter) have been seen directly in regions where stars had <a href="https://physicsworld.com/a/floating-planets-challenge-theorists/">just formed</a>. But finding smaller rogue planets proved almost impossible until “lensing” was discovered.</p>
<h2>Gravitational lensing</h2>
<p>Anything with mass bends space and causes light to deflect from a straight path. The result is that an object with mass focuses the light from a source behind it – amplifying it like a huge magnifying glass. This is called <a href="https://theconversation.com/how-we-managed-what-einstein-thought-was-impossible-and-used-his-theory-to-weigh-a-star-79050">gravitational lensing</a>. It was predicted by Einstein’s <a href="https://theconversation.com/how-einsteins-general-theory-of-relativity-killed-off-common-sense-physics-50042">general theory of relativity</a> and was <a href="https://cds.cern.ch/record/489163/files/0102462.pdf">first verified</a> when stars were seen to be displaced from their usual positions when viewed close to the Sun while it was perfectly eclipsed by the Moon in 1919.</p>
<p>The effect of gravitational lensing has been observed in galaxies made up of trillions of stars, caused by the vast amounts of stuff in between galaxies and by stars lining up with other stars in the background. One observation was caused by <a href="https://eventhorizontelescope.org/press-release-april-10-2019-astronomers-capture-first-image-black-hole">a black hole</a> in a “nearby” massive galaxy called Messier 87, in 2019. So even an “invisible” rogue planet could act as a gravitational lens – or micro-lens, as they can be so small.</p>
<p>One such “micro-lensing” event was attributed to the new rogue planet, called <a href="https://www.fuw.edu.pl/press-release/news6616.html">OGLE-2016-BLG-1928</a>. The sighting of the amplification of the light from an inconspicuous star in the dense inner regions of the Milky Way galaxy only lasted 42 minutes. </p>
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<p>This meant it had to be a small object and the estimated mass left no doubt that it had to be a planet not much different in size from Earth. The lensing planet was not found to be associated with a star. Lensing rogue planets have been <a href="https://www.aanda.org/2019-highlights/1632-two-new-free-floating-planet-candidates-from-microlensing-mroz-et-al">found before</a>, but this is one of the most convincing cases. As well as being the one most akin to Earth, OGLE-2016-BLG-1928 is also the smallest rogue ever found. </p>
<h2>Could Earth go rogue?</h2>
<p>Large numbers of rogue planets criss-crossing our galaxy raise intriguing questions. Could life have formed and survived, or settled on such worlds? Perhaps technologically advanced civilisations could overcome the inconveniences of eternal darkness and an ice age with no comparison in Earth’s long and varied history? Maybe they harnessed nuclear power or became entirely non-biological? </p>
<p>That may sound like science fiction, but what are the chances of Earth running into such a planet by chance? This is not inconceivable. Only in the last couple of years, rogue asteroids such as <a href="https://solarsystem.nasa.gov/asteroids-comets-and-meteors/comets/oumuamua/in-depth/">Oumuamua</a> and rogue comets such as <a href="https://www.nasa.gov/feature/interstellar-comet-borisov-reveals-its-chemistry-and-possible-origins/">Borisov</a> whizzed through our solar system. It is unlikely a rogue planet would pass by us that close up. But it’s not beyond the realms of probability.</p>
<p>Earth has so far escaped banishment from the Sun. But one day, in about 4bn years, Earth too could go rogue. Because as the Sun ages, swells up and blows half of itself into space, Earth will either be swallowed by it, or be forced away. But it is unlikely to escape its gravitational attraction altogether. So as the dead Sun is degraded to a smouldering white dwarf, the Earth will face a similar fate to those other dark, cold worlds. Not entirely alone, but far away from the once warm and bright orbit of its star.</p><img src="https://counter.theconversation.com/content/149588/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jacco van Loon does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Not all planets orbit stars. Rogues float through the galaxy in darkness and are almost impossible to see.Jacco van Loon, Astrophysicist and Director of Keele Observatory, Keele UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1479532020-10-22T11:21:36Z2020-10-22T11:21:36ZDark matter: our method for catching ghostly haloes could help unveil what it’s made of<figure><img src="https://images.theconversation.com/files/364959/original/file-20201022-13-1xjvrhm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Artist's conception of the Milky Way galaxy, which should contain dark matter haloes.</span> <span class="attribution"><span class="source">Nick Risinger/NASA</span></span></figcaption></figure><p>The search for <a href="https://theconversation.com/why-do-astronomers-believe-in-dark-matter-122864">dark matter</a> – an unknown and invisible substance thought to make up the vast majority of matter in the universe – is at a crossroads. Although it was proposed <a href="https://www.britannica.com/video/186454/Fritz-Zwicky-inference-dark-matter-existence">nearly 70 years ago</a> and has been searched for intensely - with large particle colliders, detectors deep underground and even instruments in space – it is still nowhere to be found. </p>
<p>But astronomers have promised <a href="https://arxiv.org/pdf/1810.01668.pdf">to leave “no stone unturned”</a> and have started to cast their net wider out into the galaxy. The idea is to extract information from astrophysical objects that may have witnessed chunks of it as they were passing by. We have just proposed <a href="https://arxiv.org/abs/2006.06741">a new method of doing so</a> by tracing galactic gas – and it may help tell us what it’s actually made of. </p>
<p>Physicists believe that dark matter has a propensity to structure itself into a hierarchy of haloes and subhaloes, via gravity. The masses of these clumps fall on a spectrum, with lower mass ones expected to be more numerous. Is there a limit to how light they could be? It depends on the nature of the dark matter particles. </p>
<h2>Warm versus cold</h2>
<p>Dark matter cannot be seen directly. We know it exists because we can see the gravitational effects it has on surrounding matter. There are <a href="https://phys.org/news/2016-08-dark-matterhot.html">different theories</a> about what dark matter may actually be. The standard model suggests it is cold, meaning it moves very slowly and only interacts with other matter through the force of gravity. This would be consistent with it being made up of particles <a href="https://theconversation.com/from-machos-to-wimps-meet-the-top-five-candidates-for-dark-matter-51516">known as axions or WIMPS</a>. Another theory, however, suggests it is warm, meaning it moves at higher speeds. One such particle candidate is the <a href="https://www.symmetrymagazine.org/article/what-could-dark-matter-be">sterile neutrino</a>.</p>
<figure class="align-center ">
<img alt="Image of the Milky Way galaxy with a dark matter halo around it." src="https://images.theconversation.com/files/364278/original/file-20201019-13-1c7seek.jpg?ixlib=rb-1.1.0&rect=11%2C0%2C3982%2C2250&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/364278/original/file-20201019-13-1c7seek.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/364278/original/file-20201019-13-1c7seek.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/364278/original/file-20201019-13-1c7seek.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/364278/original/file-20201019-13-1c7seek.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/364278/original/file-20201019-13-1c7seek.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/364278/original/file-20201019-13-1c7seek.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Artist’s impression of the expected dark matter distribution around the Milky Way, seen as a blue halo.</span>
<span class="attribution"><span class="source">ESO/L. Calçada</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>If dark matter is cold, a Milky Way-type galaxy could harbour one or two subhaloes weighing as much as 10<sup>10</sup> Suns, and most likely hundreds with masses of around 10<sup>8</sup> Suns. If dark matter is warm, haloes lighter than around 10<sup>8</sup> Suns cannot form easily. So tallying light mass dark haloes can tell us something about the nature of dark matter.</p>
<h2>Halo imprints</h2>
<p>We believe that the existence of lower mass haloes can be revealed by carefully planned observations. Astronomers have already got pretty good at this game of hide and seek with dark matter haloes and have devised observations to pick up the damage they leave behind. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/364281/original/file-20201019-13-f98uh4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/364281/original/file-20201019-13-f98uh4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/364281/original/file-20201019-13-f98uh4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/364281/original/file-20201019-13-f98uh4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/364281/original/file-20201019-13-f98uh4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/364281/original/file-20201019-13-f98uh4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/364281/original/file-20201019-13-f98uh4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A galaxy cluster with dark matter mapped in blue and bright X-rays in pink.</span>
<span class="attribution"><span class="source">Smithsonian/wikipedia</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>To date, observations have targeted mostly the changes in the distribution of stars in the Milky Way. For example, the Large Magellanic Cloud, a smaller galaxy orbiting ours, seems to have a dark matter halo which is massive enough to <a href="https://aasnova.org/2019/11/13/hunting-for-a-dark-matter-wake/">trigger an enormous wake</a> – driving the stars from across vast regions to move in unison. </p>
<p>A few of the smaller dark matter haloes thought to be whizzing inside the Milky Way may occasionally pierce through large stellar features, such as globular clusters (spherical collection of stars), leaving <a href="https://astrobites.org/2018/05/08/stellar-streams-the-nature-of-dark-matter/">tell-tale gaps</a> in them. Dark matter haloes can also affect how light bends around astrophysical objects in a process called <a href="https://academic.oup.com/mnras/article/363/4/1136/1044360">gravitational lensing</a>.</p>
<p>But the signals left in the stellar distributions are weak and prone to confusion with the stars’ own motions. Another way to probe the effect of haloes is by looking at the galactic gas it affects. Galaxies have <a href="https://www.nasa.gov/mission_pages/chandra/news/H-12-331.html">plenty of hot gas</a> (with a temperature of around 10<sup>6</sup> degrees Kelvin) which extends out to their edge, providing a wide net for catching these dark matter haloes.</p>
<p>Using a combination of analytical calculations and computer simulations, we have shown that dark haloes heavier than 10<sup>8</sup> solar masses can compress the hot gas through which they are moving. These will create local spikes in the density of the gas, which can be picked up by X-ray telescopes. These are predicted to be minute, of the order of a few per cent, but they will be within the reach of the upcoming <a href="https://wwwastro.msfc.nasa.gov/lynx/">Lynx</a> and <a href="https://www.the-athena-x-ray-observatory.eu/">Athena</a> telescopes.</p>
<p>Our models also predict that the spikes in the density of the <a href="https://www.nasa.gov/feature/goddard/2020/hubble-maps-giant-halo-around-andromeda-galaxy">cooler galactic gas</a> (with temperature of around 10<sup>5</sup> K) will be even more significant. This means that the cooler gas can record the passage of dark matter haloes even more sensitively than the hot gas.</p>
<p>Another promising way of observing the dark-matter-induced fluctuations in the gas is via the photons (light particles) from the cosmic microwave background – the light left over from the Big Bang. This light <a href="https://en.wikipedia.org/wiki/Sunyaev%E2%80%93Zeldovich_effect">scatters off</a> the highly energetic electrons in the hot gas in a way that we can detect, providing a complementary approach to the other studies. </p>
<p>Over the next few years, this new method can be used to test models of dark matter. Regardless of whether dark matter haloes below 10<sup>8</sup> solar masses are found in the numbers predicted or not, we will learn something useful. If the numbers match up, the standard cosmological model would have passed an important test. If they are missing, or are far fewer than expected, the standard model would be ruled out and we’ll have to find a more viable alternative. </p>
<p>Dark matter remains a mystery, but there’s a huge amount of work going into solving it. Whether the answer will come from instruments on Earth or astrophysical probes, it will no doubt be one of the most important discoveries of the century.</p><img src="https://counter.theconversation.com/content/147953/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andreea Font does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>A new method suggests we should aim to detect dark matter haloes by tracing galactic gas.Andreea Font, Astrophysicist, Liverpool John Moores UniversityLicensed as Creative Commons – attribution, no derivatives.