tag:theconversation.com,2011:/es/topics/astronomy-50/articlesAstronomy – The Conversation2024-03-28T12:50:48Ztag:theconversation.com,2011:article/2257712024-03-28T12:50:48Z2024-03-28T12:50:48ZNASA’s mission to an ice-covered moon will contain a message between water worlds<figure><img src="https://images.theconversation.com/files/584594/original/file-20240326-30-7p4fl7.jpg?ixlib=rb-1.1.0&rect=7%2C8%2C1191%2C1212&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">An illustration of the Europa Clipper spacecraft, which will head to Jupiter's moon Europa. </span> <span class="attribution"><a class="source" href="https://europa.nasa.gov/resources/173/europa-clipper-journey-to-an-ocean-world-poster/">NASA/JPL-Caltech</a></span></figcaption></figure><p>NASA’s <a href="https://europa.nasa.gov/">Europa Clipper</a> spacecraft, <a href="https://theconversation.com/jupiters-moons-hide-giant-subsurface-oceans-two-missions-are-sending-spacecraft-to-see-if-these-moons-could-support-life-203207">headed to Jupiter’s ice-covered moon</a> Europa in October 2024, will carry <a href="https://europa.nasa.gov/spacecraft/vault-plate/">a laser-etched message</a> that celebrates humanity’s connection to water. The message pays homage to past NASA missions that carried similar messages. </p>
<p>As <a href="https://meti.org/en/board/douglas-vakoch">the president</a> of <a href="https://meti.org/mission">Messaging Extraterrestrial Intelligence, or METI, International</a>, I helped design the message on Clipper with two fellow members of our board of directors: linguists <a href="https://meti.org/en/board/sheri-wells-jensen">Sheri Wells-Jensen</a> and <a href="https://longnow.org/people/laura/">Laura Buszard-Welcher</a>. METI International is a scientific organization dedicated to transmitting powerful radio messages to extraterrestrial life.</p>
<p>We collected audio recordings in 103 languages, and we decided how to <a href="https://europa.nasa.gov/spacecraft/vault-plate/#otp_waveform_generator">convert these into waveforms</a> that show these sounds visually. Colleagues from NASA etched these waveforms into the metal plate that shields the spacecraft’s sensitive electronics from <a href="https://www.astronomy.com/science/what-is-the-source-of-jupiters-radiation/">Jupiter’s harsh radiation</a>. </p>
<p>I also designed another part of the message that visually depicts the wavelengths of water’s constituents, because water is so important to the search for intelligent life in the universe. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/8coGQ9kvBas?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">NASA’s design for the Clipper message heading to Jupiter’s moon Europa.</span></figcaption>
</figure>
<p>Etching messages into spacecraft isn’t a new practice, and Clipper’s message fits into a decades-old tradition started by <a href="https://www.britannica.com/biography/Carl-Sagan">astronomer Carl Sagan</a>.</p>
<p>In 1972 and 1973, two Pioneer spacecraft headed to Jupiter and Saturn carrying metal plaques engraved with scientific and pictorial messages. In 1977, two <a href="https://theconversation.com/what-the-voyager-space-probes-can-teach-humanity-about-immortality-and-legacy-as-they-sail-through-space-for-trillions-of-years-177513">Voyager spacecraft</a> headed to Jupiter, Saturn, Uranus and Nepture bearing <a href="https://theconversation.com/voyager-golden-records-40-years-later-real-audience-was-always-here-on-earth-79886">gold-plated copper phonograph records</a>. These records contained tutorials in mathematics and chemistry, as well as music, photos and sounds of Earth and greetings in 55 languages.</p>
<h2>Water words</h2>
<p>As water is essential for life on Earth, searching for its presence elsewhere has been key to many NASA missions. Astronomers <a href="https://science.nasa.gov/jupiter/moons/europa/">suspect that Europa</a>, where Clipper is headed, <a href="https://theconversation.com/jupiters-moons-hide-giant-subsurface-oceans-two-missions-are-sending-spacecraft-to-see-if-these-moons-could-support-life-203207">has an ocean underneath its icy surface</a>, making it a prime candidate for the search for life in the outer solar system.</p>
<p>Part of the Clipper message features the word for water in 103 languages. We started with audio files collected online, but we then needed to analyze those and find an output that could be engraved on a metal plate. I ended up going back to some of the techniques I used in some of my early psycholinguistic research, where I explored how <a href="https://doi.org/10.1121/1.408973">emotions are encoded in speech</a>.</p>
<p>The 103 spoken words we recorded represent a global snapshot of the diversity of Earth’s languages. The outward-facing side of the Clipper plate shows the words as waveforms that track the varying intensity of sound as each word is spoken. </p>
<p>Each person whom we recorded saying the word “water” for the waveform had a connection to water. For example, the lawyer who contributed the word for water in Uzbek – “suv” – organizes an annual music festival in Uzbekistan to raise awareness of the desertification of the Aral Sea. </p>
<p>The native speaker of the Catalan water word – “aigua” – hunts <a href="https://theconversation.com/nasas-tess-spacecraft-is-finding-hundreds-of-exoplanets-and-is-poised-to-find-thousands-more-122104">for exoplanets</a>, discovering potentially habitable planets that orbit other stars. </p>
<h2>The Drake Equation</h2>
<p>Clipper’s message also pays homage to <a href="https://www.seti.org/frank-drake">astronomer Frank Drake</a>, the father of SETI – <a href="https://www.seti.org/">the Search for Extraterrestrial Intelligence</a> – by bearing <a href="https://www.seti.org/drake-equation-index">the Drake Equation</a>, his namesake formula. By drawing on scientific data, as well as some best guess hunches, the Drake Equation estimates the number of extraterrestrial civilizations in the galaxy currently sending messages into the cosmos. </p>
<p>By one <a href="https://www.britannica.com/science/Drake-equation">widely quoted estimate</a>, there are a tenth as many of these extraterrestrial civilizations as one’s average lifetime in years. If civilizations survive for a million years, for example, there should be about 100,000 in the galaxy. If they last only a century on average, scientists would estimate that about 10 exist.</p>
<p>Radio astronomers study the universe by examining the radiation that chemical elements in space give off. They spend much of their time mapping the distribution of the most abundant chemical in the universe – hydrogen.</p>
<p>Hydrogen emits radiation at a certain frequency called the <a href="http://www.setileague.org/askdr/hydrogen.htm">hydrogen line</a>, which radio telescopes can detect. During <a href="https://www.seti.org/project-ozma">Project Ozma</a>, the first modern-day SETI experiment, Drake looked for artificial signals at the same frequency, because he figured scientists on other worlds might recognize hydrogen as universally significant and broadcast signals at that frequency.</p>
<h2>The water hole</h2>
<p>As our team developed our water words message, I realized that the message would only make sense if it were discovered by someone already familiar with the contents inscribed on the plate. The Drake Equation would only make sense if someone already knew what each of the terms in the equation stood for. </p>
<p>The Europa Clipper will crash into Jupiter or one of its other moons, with <a href="https://www.space.com/europa-clipper-might-crash-into-ganymede">Ganymede or Callisto the leading candidates</a>. But if for some reason the mission changes and it survives that fate, then humans far in the future with a radically different cultural background and different language conventions may retrieve it millennia from now as an ancient artifact.</p>
<p>To ensure we had at least one part of the message that a distant future scientist might be able to understand, I also designed a pictorial representation of the same frequency that Drake used for Project Ozma: the hydrogen line. We engraved this on the Clipper plate, along with a frequency called the hydroxyl line.</p>
<p>When hydrogen (H+) and <a href="https://www.sciencedirect.com/topics/chemistry/hydroxyl">hydroxyl (OH-)</a> combine, they form water. Scientists call the range of frequencies between these lines the “<a href="http://www.setileague.org/general/waterhol.htm">water hole</a>.” The water hole represents the part of the radio spectrum where astronomers conducted the first SETI experiments.</p>
<p>We displayed the hydrogen and hydroxyl lines using their wavelengths in the Clipper message. The metal plate also has diagrams showing what hydrogen and hydroxyl look like at the atomic level. </p>
<p>We’re hoping that future chemists would recognize these chemical components as the ingredients of water. If they do, we will have succeeded in communicating at least a few core scientific concepts across time, space and language. </p>
<p>Waveforms let our team tie the messages on the two sides of the Clipper plate together. On the water words side, over a hundred words are depicted by their waveforms. On the other side, the wavelengths of hydrogen and hydroxyl – the constituents of water – are etched into the plate.</p>
<p>METI International funded the collection and curation of the water words, as well as my design of the hydrogen and hydroxyl lines, providing these to NASA at no cost.</p>
<p>While designing the message for the Europa Clipper, we got to reflect on the importance of water on Earth, and think about why astronomers feel so compelled to search for it beneath the icy crust of Jupiter’s moon Europa. The spacecraft is scheduled to enter Jupiter’s orbit in April 2030.</p><img src="https://counter.theconversation.com/content/225771/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Douglas Vakoch does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Europa Clipper will contain a plaque that celebrates humanity’s relationship with water and a decades-old tradition of searching for life outside Earth.Douglas Vakoch, President, METI International; Professor Emeritus, California Institute of Integral StudiesLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2267292024-03-27T23:55:16Z2024-03-27T23:55:16ZA cosmic ‘speed camera’ just revealed the staggering speed of neutron star jets in a world first<figure><img src="https://images.theconversation.com/files/584904/original/file-20240327-26-ntaiw6.jpg?ixlib=rb-1.1.0&rect=1283%2C180%2C5431%2C3798&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Nuclear explosions on a neutron star feed its jets.
</span> <span class="attribution"><span class="source">Danielle Futselaar and Nathalie Degenaar, Anton Pannekoek Institute, University of Amsterdam</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>How fast can a neutron star drive powerful jets into space? The answer, it turns out, is about one-third the speed of light, as our team has just revealed in a <a href="https://www.nature.com/articles/s41586-024-07133-5">new study</a> published in Nature.</p>
<p>Energetic cosmic beams known as <a href="https://www.britannica.com/science/radio-jet">jets</a> are seen throughout our universe. They are launched when material – mainly dust and gas – falls in towards any dense central object, such as a neutron star (an extremely dense remnant of a once-massive star) or a <a href="https://science.nasa.gov/universe/black-holes/">black hole</a>. </p>
<p>The jets carry away some of the gravitational energy released by the infalling gas, recycling it back into the surroundings on far larger scales.</p>
<p>The most powerful jets in the universe come from the biggest black holes at the centres of galaxies. The energy output of these jets can affect the evolution of an entire galaxy, or even a galaxy cluster. This makes jets a critical, yet intriguing, component of our universe.</p>
<p>Although jets are common, we still don’t fully understand how they are launched. Measuring the jets from a neutron star has now given us valuable information.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-brightest-object-in-the-universe-is-a-black-hole-that-eats-a-star-a-day-222612">The brightest object in the universe is a black hole that eats a star a day</a>
</strong>
</em>
</p>
<hr>
<h2>Jets from stellar corpses</h2>
<p>Jets from black holes tend to be bright, and have been well studied. However, the jets from neutron stars are typically much fainter, and much less is known about them.</p>
<p>This presents a problem, since we can learn a lot by comparing the jets launched by different celestial objects. <a href="https://imagine.gsfc.nasa.gov/science/objects/neutron_stars1.html">Neutron stars</a> are extremely dense stellar corpses – cosmic cinders the size of a city, yet containing the mass of a star. We can think of them as enormous atomic nuclei, each about 20 kilometres across.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/M8DmwNvtfxk?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>In contrast to black holes, neutron stars have both a solid surface and a magnetic field, and gas falling onto them releases less gravitational energy. All of these properties will have an effect on how their jets are launched, making studies of neutron star jets particularly valuable.</p>
<p>One key clue to how jets are launched comes from their speeds. If we can determine how jet speeds vary with the mass or spin of the neutron star, that would provide a powerful test of theoretical predictions. But it is extremely challenging to measure jet speeds accurately enough for such a test.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/unexpected-find-from-a-neutron-star-forces-a-rethink-on-radio-jets-103843">Unexpected find from a neutron star forces a rethink on radio jets</a>
</strong>
</em>
</p>
<hr>
<h2>A cosmic speed camera</h2>
<p>When we measure speeds on Earth, we time an object between two points. This could be a 100-metre sprinter running down the track, or a point-to-point speed camera tracking a car.</p>
<p>Our team, led by Thomas Russell from the <a href="http://www.inaf.it/en">Italian National Institute of Astrophysics</a> in Palermo, conducted a new experiment to do this for neutron star jets.</p>
<p>What has made this measurement so difficult in the past is that jets are steady flows. This means there is no single starting point for our timer. But we were able to identify a short-lived signal at X-ray wavelengths that we could use as our “starting gun”.</p>
<p>Being so dense, neutron stars can “steal” matter from a nearby orbiting companion star. While some of that gas is launched outwards as jets, most of it ends up falling onto the neutron star. As the material piles up, it gets hotter and denser.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/DU43sUjGeL4?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>When enough material has built up, it triggers a thermonuclear explosion. A runaway nuclear fusion reaction occurs and rapidly spreads to engulf the entire star. The fusion lasts for a few seconds to minutes, causing a short-lived <a href="https://www.nasa.gov/universe/nasas-nicer-catches-record-setting-x-ray-burst/">burst of X-rays</a>.</p>
<h2>One step closer to solving a mystery</h2>
<p>We thought this thermonuclear explosion would disrupt the neutron star’s jets. So, we used CSIRO’s <a href="https://www.csiro.au/en/about/facilities-collections/atnf/australia-telescope-compact-array">Australia Telescope Compact Array</a> to stare at the jets for three days at radio wavelengths to try and catch the disruption. At the same time, we used the European Space Agency’s <a href="https://www.esa.int/Science_Exploration/Space_Science/Integral_overview">Integral</a> telescope to look at the X-rays from the system.</p>
<p>To our surprise, we found the jets got brighter after every pulse of X-rays. Instead of disrupting the jets, the thermonuclear explosions seemed to power them up. And this pattern was repeated ten times in one neutron star system, and then again in a second system.</p>
<p>We can explain this surprising result if the X-ray pulse causes gas swirling around the neutron star to fall inwards more quickly. This, in turn, provides more energy and material to divert into the jets.</p>
<p>Most importantly, however, we can use the X-ray burst to indicate the launch time of the jets. We timed how long they took to move outwards to where they became visible at two different radio wavelengths. These start and finish points provided us with our cosmic speed camera.</p>
<p>Interestingly, the jet speed we measured was close to the “escape speed” from a neutron star. On Earth, this escape speed is <a href="https://www.britannica.com/science/escape-velocity">11.2 kilometres per second</a> – what rockets need to achieve to break free of Earth’s gravity. For a neutron star, that value is around half the speed of light.</p>
<p>Our work has introduced a new technique for measuring neutron star jet speeds. Our next steps will be to see how the jet speed changes for neutron stars with different masses and rotation rates. That will allow us to directly test theoretical models, taking us one step closer to figuring out how such powerful cosmic jets are launched.</p><img src="https://counter.theconversation.com/content/226729/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>James Miller-Jones receives funding from the Australian Research Council and the Western Australian State Government.</span></em></p>Powerful jets are launched from the most massive objects in our universe, but we don’t fully understand how. This measurement gets us a step closer to solving the mystery.James Miller-Jones, Professor, Curtin UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2258662024-03-27T17:09:15Z2024-03-27T17:09:15ZThe April 8 eclipse provides a rare opportunity to witness the sun’s superhot corona<figure><img src="https://images.theconversation.com/files/584383/original/file-20240326-16-cpzqx3.jpg?ixlib=rb-1.1.0&rect=0%2C2%2C1888%2C1057&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The corona of the sun can be clearly seen in this image taken in 2007.</span> <span class="attribution"><a class="source" href="https://images.nasa.gov/details/PIA09320">(NASA/JPL-Caltech/NRL/GSFC)</a></span></figcaption></figure><p>Being within a narrow path across Mexico, the United States and eastern Canada on April 8 will give a rare chance to see the hottest thing any human ever sees: the corona surrounding the sun.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/on-april-8-2024-parts-of-ontario-quebec-the-maritimes-and-newfoundland-will-see-a-total-eclipse-of-the-sun-heres-how-to-get-ready-for-it-203382">On April 8, 2024, parts of Ontario, Québec, the Maritimes and Newfoundland will see a total eclipse of the sun. Here's how to get ready for it.</a>
</strong>
</em>
</p>
<hr>
<p>The word “corona” means “crown” — during the eclipse, it becomes visible, and streaming plasma leaving the sun appears in amazing patterns.</p>
<p>This outer atmosphere shines with a strange whitish light, and is safe to look at once the bright surface of the sun is fully obscured. However, it is not safe to look at partial phases of the eclipse without <a href="https://theconversation.com/total-solar-eclipses-while-stunning-can-damage-your-eyes-if-viewed-without-the-right-protection-221381">suitable eye protection</a> such as an approved filter or a <a href="https://svs.gsfc.nasa.gov/14391/">shadow box</a>. </p>
<p>Humankind has been awed by this spectacle <a href="https://www.wired.com/2008/05/may-28-585-bc-predicted-solar-eclipse-stops-battle/">for a very long time without understanding it</a>. Astronomers now know the sun’s corona is heated to up to <a href="https://www.nasa.gov/science-research/heliophysics/nasas-parker-solar-probe-and-the-curious-case-of-the-hot-corona/">two million degrees Kelvin</a>, numerically almost equivalent to Celsius for such high temperatures. </p>
<p>What astronomers haven’t figured out yet is why the corona is so hot.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/ykkrf87WsLI?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">NASA scientists describe photographing the sun’s corona during the 2015 eclipse.</span></figcaption>
</figure>
<h2>Heat and density</h2>
<p>The surface of the sun has a temperature of <a href="https://scied.ucar.edu/learning-zone/sun-space-weather/surface-of-the-sun">only about 5,800 kelvins</a> (5,500 C). The reason that we can safely look at the corona but must avoid looking at the surface has to do with density: <a href="https://spaceplace.nasa.gov/sun-corona/en/">the corona is very thin</a>, and most of the light we see is reflected sunlight from the surface. </p>
<p>The sun’s surface has enough density that, at its temperature, it emits about <a href="https://www.pveducation.org/pvcdrom/properties-of-sunlight/solar-radiation-in-space">65 megawatts for each square meter</a>. Even diluted by <a href="https://earthsky.org/space/what-is-the-astronomical-unit/">distance from the sun of 150 million kilometres</a>, this is enough to cause immediate eye damage.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/total-solar-eclipses-while-stunning-can-damage-your-eyes-if-viewed-without-the-right-protection-221381">Total solar eclipses, while stunning, can damage your eyes if viewed without the right protection</a>
</strong>
</em>
</p>
<hr>
<p>Since the corona is such thin gas, despite its high temperature, it does not emit nor reflect much light. For this reason, we can see it only when the body of the sun is completely blocked by the moon. Otherwise the scattered light in our atmosphere completely overwhelms it.</p>
<p>The mystery of the corona’s heat <a href="https://www.americanscientist.org/article/revealing-the-true-solar-corona">puzzled 19th-century astronomers</a>. At the time, new instruments had been developed to study <a href="https://www.azooptics.com/Article.aspx?ArticleID=1984">the composition of celestial bodies</a>.</p>
<p>In 1704, Sir Isaac Newton had discovered that “white” light could be split into colors, a result <a href="https://library.si.edu/digital-library/book/optickstreatise00newta">published in <em>Opticks</em></a>. Unfortunately, his basic views about light were wrong and likely set back the development of optical science 100 years! </p>
<p>Only in the early 1800s were instruments developed, largely setting the stage for the <a href="https://www.zeiss.com/corporate/en/about-zeiss/past/history/locations.html">immensely profitable German optical industry</a>. This allowed scientists to find out what materials were made of by the light they emitted when heated. </p>
<p>A staple of such studies was the <a href="https://www.britannica.com/science/Bunsen-burner">Bunsen burner</a>, originally developed not to have a colour like other flames do.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/582669/original/file-20240318-16-fmoksh.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="a black circle surrounded by wispy white light against a navy background" src="https://images.theconversation.com/files/582669/original/file-20240318-16-fmoksh.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/582669/original/file-20240318-16-fmoksh.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=430&fit=crop&dpr=1 600w, https://images.theconversation.com/files/582669/original/file-20240318-16-fmoksh.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=430&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/582669/original/file-20240318-16-fmoksh.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=430&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/582669/original/file-20240318-16-fmoksh.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=540&fit=crop&dpr=1 754w, https://images.theconversation.com/files/582669/original/file-20240318-16-fmoksh.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=540&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/582669/original/file-20240318-16-fmoksh.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=540&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 total solar eclipse in 2015 over Svalbard, Norway, reveals the streaming shapes in the solar wind pillars.</span>
<span class="attribution"><span class="source">(M. Druckmüller, S. Habbal, P. Aniol, P. Štarha)</span></span>
</figcaption>
</figure>
<h2>Photography and astrophysics</h2>
<p>The parallel development of photography also helped <a href="https://history.aip.org/exhibits/cosmology/tools/tools-spectroscopy.htm">astronomy to turn into the science of astrophysics</a>, and the sun was an ideal first target for early instruments due to being very bright. </p>
<p>During the solar eclipse of 1868, emissions like the bright red known to be <a href="https://skyandtelescope.org/observing/guide-to-observing-the-sun-in-h-alpha092321050923/">from hydrogen were observed</a>. But when this light was broken down with a spectroscope, it also showed a yellow light that had never been observed on Earth. </p>
<p>This was determined to be a new element, named for its association with the sun (Greek <em>helios</em>). Only in 1895 was helium found on Earth, and in the strangest of places: <a href="https://www.smithsonianmag.com/history/how-scientists-discovered-helium-first-alien-element-1868-180970057/">radioactive ores</a>. </p>
<p>Almost all helium now used on Earth comes from natural gas fields, where it is trapped as it comes up from uranium and other decaying radioactive ores. The helium in the sun later became strong evidence for the Big Bang, in which the first nuclei, which were hydrogen, quickly underwent nuclear fusion to produce helium, but its discovery in the sun set the stage for expecting new elements there.</p>
<h2>A new mystery</h2>
<p>Once spectroscopy developed further in the late 19th century, indeed another mystery arose. Many elements had been discovered on Earth and put in systematic order by Russian chemist Dmitri Mendeleev as the “<a href="https://pubchem.ncbi.nlm.nih.gov/periodic-table">periodic table</a>.”</p>
<p>Surprisingly, many elements were also detected in solar spectra, usually when they absorbed specific wavelengths from the pure light coming from deep layers in the sun, <a href="https://imagine.gsfc.nasa.gov/science/toolbox/spectra1.html">leaving absorption lines</a>. Although the sun is made mostly of hydrogen and helium, these are not prominent in its spectrum. </p>
<p>However, in the corona, completely unknown lines were found. Following the lead of helium, it was felt that the sun must contain an element never observed on Earth, <a href="https://sunearthday.nasa.gov/2006/locations/coronium.php">promptly dubbed coronium</a>. Only in the 1940s was it realized that the emissions actually came from familiar elements, including iron. These were not initially recognized due to being highly stripped of the normal number of electrons going around their nuclei (normally 26 in iron), indicating extreme temperatures that rip atoms apart. </p>
<p>Even stranger, the further out one observed from the sun, the hotter the corona became.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/582445/original/file-20240318-20-t6q0rt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="a black circle surrounded by wisps of red and green" src="https://images.theconversation.com/files/582445/original/file-20240318-20-t6q0rt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/582445/original/file-20240318-20-t6q0rt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=441&fit=crop&dpr=1 600w, https://images.theconversation.com/files/582445/original/file-20240318-20-t6q0rt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=441&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/582445/original/file-20240318-20-t6q0rt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=441&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/582445/original/file-20240318-20-t6q0rt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=554&fit=crop&dpr=1 754w, https://images.theconversation.com/files/582445/original/file-20240318-20-t6q0rt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=554&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/582445/original/file-20240318-20-t6q0rt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=554&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 2015 eclipse imaged in the light given off by highly ionized iron. The red indicates a temperature about one million degrees C, green about two million degrees C.</span>
<span class="attribution"><a class="source" href="https://doi.org/10.3847/2041-8213/abe775">(SOURCE)</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Solar winds and weather</h2>
<p>In the late 1950s, the physicist Eugene Parker found that such high temperatures for the solar corona meant that it could not be static: it had to <a href="https://news.uchicago.edu/explainer/what-is-solar-wind">be blowing off into space</a>. This prediction was verified by <a href="http://www.phy6.org/Education/whsolwi.html">spacecraft measurements in 1959</a>. </p>
<p>Since then, we have known that there is a solar wind, and that the magnetic field shown by coronal structures is carried off into space with it. The solar wind can bring energy to Earth, which penetrates near us when the magnetic field is opposed to that of our planet, bringing auroras and potentially hazardous “<a href="https://theconversation.com/space-weather-is-difficult-to-predict-with-only-an-hour-to-prevent-disasters-on-earth-159895">space weather</a>.”</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/larger-and-more-frequent-solar-storms-will-make-for-potential-disruptions-and-spectacular-auroras-on-earth-219183">Larger and more frequent solar storms will make for potential disruptions and spectacular auroras on Earth</a>
</strong>
</em>
</p>
<hr>
<p>NASA’s <a href="https://science.nasa.gov/mission/parker-solar-probe/">Parker Solar Probe</a> is now nearing the inner regions of the corona, still trying to determine the exact origins of the solar wind. Parker, who passed away in 2022, saw initial results from this spacecraft trying to find exactly how the outrageously hot corona propels the solar wind. </p>
<p>Meanwhile, April 8 is a rare opportunity to safely view the sun’s glorious super-heated corona.</p><img src="https://counter.theconversation.com/content/225866/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Martin Connors receives funding from NSERC. </span></em></p>The solar corona can be seen during the solar eclipse on April 8. Astronomers are still trying to figure out the mysteries of the corona, including why it’s so hot.Martin Connors, Professor of Space Science and Physics, Athabasca UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2265582024-03-27T17:07:01Z2024-03-27T17:07:01ZThe total solar eclipse in North America could help shed light on a persistent puzzle about the Sun<figure><img src="https://images.theconversation.com/files/584141/original/file-20240325-24-ot473c.jpg?ixlib=rb-1.1.0&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/totality-during-2023-australian-total-solar-2344355767">aeonWAVE / Shutterstock</a></span></figcaption></figure><p>A <a href="https://science.nasa.gov/eclipses/types/#hds-sidebar-nav-1">total solar eclipse</a> takes place on <a href="https://science.nasa.gov/eclipses/future-eclipses/eclipse-2024/">April 8 across North America</a>. These events occur when the Moon passes between the Sun and Earth, completely blocking the Sun’s face. This plunges observers into a darkness similar to dawn or dusk.</p>
<p>During the upcoming eclipse, the path of totality, where observers experience the darkest part of the Moon’s shadow (the umbra), crosses Mexico, arcing north-east through Texas, the Midwest and briefly entering Canada before ending in Maine.</p>
<p>Total solar eclipses occur roughly <a href="https://www.nhm.ac.uk/discover/solar-eclipse-guide.html">every 18 months at some location on Earth</a>. The last total solar eclipse that crossed the US took place on August 21 2017. </p>
<p>An international team of scientists, led by Aberystwyth University, will be conducting experiments from <a href="https://www.fox4news.com/news/2024-eclipse-dallas-crowds-traffic">near Dallas</a>, at a location in the path of totality. The team consists of PhD students and researchers from Aberystwyth University, Nasa Goddard Space Flight Center in Maryland, and Caltech (California Institute of Technology) in Pasadena. </p>
<p>There is valuable science to be done during eclipses that is comparable to or better than what we can achieve via space-based missions. Our experiments may also shed light on a longstanding puzzle about the outermost part of the Sun’s atmosphere – its corona.</p>
<figure class="align-center ">
<img alt="Eclipse shadow" src="https://images.theconversation.com/files/584503/original/file-20240326-18-9yqs13.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/584503/original/file-20240326-18-9yqs13.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/584503/original/file-20240326-18-9yqs13.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/584503/original/file-20240326-18-9yqs13.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/584503/original/file-20240326-18-9yqs13.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/584503/original/file-20240326-18-9yqs13.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/584503/original/file-20240326-18-9yqs13.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">The path of eclipse totality passes through Mexico, the US and Canada.</span>
<span class="attribution"><a class="source" href="https://svs.gsfc.nasa.gov/5186/">NASA's Scientific Visualization Studio</a></span>
</figcaption>
</figure>
<p>The Sun’s intense light is blocked by the Moon during a total solar eclipse. This means that we can observe the <a href="https://solarscience.msfc.nasa.gov/corona.shtml">Sun’s faint corona</a> with incredible clarity, from distances very close to the Sun, out to several solar radii. One radius is the distance equivalent to half the Sun’s diameter, about 696,000km (432,000 miles).</p>
<p>Measuring the corona is extremely difficult without an eclipse. It requires a special telescope <a href="https://www.space.com/what-is-a-coronagraph.html">called a coronagraph</a> that is designed to block out direct light from the Sun. This allows fainter light from the corona to be resolved. The clarity of eclipse measurements surpasses even coronagraphs based in space.</p>
<p>We can also observe the corona on a relatively small budget, compared to, for example, spacecraft missions. A persistent puzzle about the corona is the observation <a href="https://agupubs.onlinelibrary.wiley.com/doi/10.1002/9781119815600.ch2">that it is much hotter</a> than the photosphere (the visible surface of the Sun). As we move away from a hot object, the surrounding temperature should decrease, not increase. How the corona is heated to such high temperatures is one question we will investigate.</p>
<figure class="align-center ">
<img alt="Solar eclipse." src="https://images.theconversation.com/files/584507/original/file-20240326-20-xairh2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/584507/original/file-20240326-20-xairh2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=390&fit=crop&dpr=1 600w, https://images.theconversation.com/files/584507/original/file-20240326-20-xairh2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=390&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/584507/original/file-20240326-20-xairh2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=390&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/584507/original/file-20240326-20-xairh2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=490&fit=crop&dpr=1 754w, https://images.theconversation.com/files/584507/original/file-20240326-20-xairh2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=490&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/584507/original/file-20240326-20-xairh2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=490&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-vector/solar-eclipse-diagram-1146598682">Andramin / Shutterstock</a></span>
</figcaption>
</figure>
<p>We have two main scientific instruments. The first of these is Cip (coronal imaging polarimeter). Cip is also the Welsh word for “glance”, or “quick look”. The instrument takes images of the Sun’s corona with a polariser. </p>
<p>The light we want to measure from the corona is highly polarised, which means it is made up of waves that vibrate in a single geometric plane. A polariser is a filter that lets light with a particular polarisation pass through it, while blocking light with other polarisations. </p>
<p>The Cip images will allow us to measure fundamental properties of the corona, such as its density. It will also shed light on phenomena such as the solar wind. This is a stream of sub-atomic particles in the form of plasma – superheated matter – flowing continuously outward from the Sun. Cip could help us identify sources in the Sun’s atmosphere for certain solar wind streams.</p>
<p>Direct measurements of the magnetic field in the Sun’s atmosphere are difficult. But the eclipse data should allow us to study its fine-scale structure and trace the field’s direction. We’ll be able to see how far magnetic structures called large “closed” magnetic loops extend from the Sun. This in turn will give us information about large-scale magnetic conditions in the corona.</p>
<figure class="align-center ">
<img alt="Coronal loops." src="https://images.theconversation.com/files/584489/original/file-20240326-24-zlpsmc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/584489/original/file-20240326-24-zlpsmc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=442&fit=crop&dpr=1 600w, https://images.theconversation.com/files/584489/original/file-20240326-24-zlpsmc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=442&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/584489/original/file-20240326-24-zlpsmc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=442&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/584489/original/file-20240326-24-zlpsmc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=555&fit=crop&dpr=1 754w, https://images.theconversation.com/files/584489/original/file-20240326-24-zlpsmc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=555&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/584489/original/file-20240326-24-zlpsmc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=555&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Coronal loops are found around sunspots and in active regions of the Sun.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/image-article/coronal-loops-an-active-region-of-sun/">NASA/Solar Dynamics Observatory</a></span>
</figcaption>
</figure>
<p>The second instrument is Chils (coronal high-resolution line spectrometer). It collects high-resolution spectra, where light is separated into its component colours. Here, we are looking for a particular spectral signature of iron emitted from the corona. </p>
<p>It comprises three spectral lines, where light is emitted or absorbed in a narrow frequency range. These are each generated at a different range of temperatures (in the millions of degrees), so their relative brightness tells us about the coronal temperature in different regions. </p>
<p>Mapping the corona’s temperature informs advanced, computer-based models of its behaviour. These models must include mechanisms for how the coronal plasma is heated to such high temperatures. Such mechanisms might include the conversion of magnetic waves to thermal plasma energy, for example. If we show that some regions are hotter than others, this can be replicated in models. </p>
<p>This year’s eclipse also occurs during a time of heightened solar activity, so we could observe a <a href="https://www.swpc.noaa.gov/phenomena/coronal-mass-ejections">coronal mass ejection (CME)</a>. These are huge clouds of magnetised plasma that are ejected from the Sun’s atmosphere into space. They can affect infrastructure near Earth, causing problems for vital satellites. </p>
<p>Many aspects of CMEs are poorly understood, including their early evolution near the Sun. Spectral information on CMEs will allow us to gain information on their thermodynamics, and their velocity and expansion near the Sun.</p>
<p>Our eclipse instruments have recently been proposed for a space mission called <a href="https://www.surrey.ac.uk/research-projects/feasibility-study-moon-enabled-sun-occultation-mission-mesom">Moon-enabled solar occultation mission (Mesom)</a>. The plan is to orbit the Moon to gain more frequent and extended eclipse observations. It is being planned as a UK Space Agency mission involving several countries, but led by University College London, the University of Surrey and Aberystwyth University.</p>
<p>We will also have an advanced commercial 360-degree camera to collect video of the April 8 eclipse and the observing site. The video is valuable for public outreach events, where we highlight the work we do, and helps to generate public interest in our local star, the Sun.</p><img src="https://counter.theconversation.com/content/226558/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Huw Morgan 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>The eclipse will allow scientists to get rare measurements of the Sun’s atmosphere.Huw Morgan, Reader in Physical Sciences, Aberystwyth UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2263612024-03-22T14:32:05Z2024-03-22T14:32:05ZStellar murder: when stars destroy and eat their own planets<figure><img src="https://images.theconversation.com/files/583649/original/file-20240322-22-txhykg.jpg?ixlib=rb-1.1.0&rect=3%2C0%2C1036%2C584&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.nasa.gov/missions/chandra/nasas-chandra-planets-can-be-anti-aging-formula-for-stars/">NASA/CXC/M.Weiss</a></span></figcaption></figure><p>Our Sun is both our best friend and our worst enemy. On the one hand, we owe our very existence to our star. Earth and the other planets in the Solar System formed out of the same cloud of gas and dust as the Sun. </p>
<p>And without its light, there could be no life on this planet. On the other hand, there will come a day when the Sun ends all life on Earth and, eventually, destroys Earth itself.</p>
<p>The risks that stars can pose to their planets are highlighted by <a href="https://www.nature.com/articles/d41586-024-00847-6">a new study published in Nature</a>. The authors looked at stars similar to our Sun and found that at least one in 12 stars exhibits traces of metals in its atmosphere. These are thought to be the scars of planets and asteroids that have been ingested by the stars. </p>
<p>Planets should never feel too comfortable as they orbit their parent star, as there are at least two ways in which their star can betray their trust and bring about their violent demise. </p>
<h2>Tidal disruption</h2>
<p>The first is through a process called “tidal disruption”. As a planetary system forms, some planets will find themselves orbiting their star along paths that are either not quite circular or are slightly inclined relative to the plane of the star’s rotation. When that happens, the gravitational force exerted by the star on the planet will slowly correct the shape or the alignment of the wayward planet’s orbit. </p>
<p>In extreme cases, the gravitational force applied by the star will destabilise the planet’s orbit, slowly pulling it closer and closer. If the hapless planet strays too close, it will be torn apart by the star’s gravity. This happens because the side of the planet facing the star is slightly closer than the side facing away (the difference is the planet’s diameter). </p>
<p>The strength of the gravitational pull exerted by the star depends on the distance between it and the planet, so that the side of the planet facing the star feels a slightly stronger pull than the side facing away. </p>
<p>On Earth, this difference in the strength of the force of gravity creates the daily ebb and flow of the tides. In essence, the Sun is trying to deform Earth, but is far enough away that it only manages to pull on the waters of its oceans. But a planet dangerously close to its star will find its very crust and core being pulled apart by these tides. </p>
<p>If the planet is not too close to the star, its shape will merely be deformed into that of an egg. Just a little closer to the star, and the difference between the gravitational pull on its different sides will be enough to completely tear it apart, reducing it back to a cloud of gas and dust that spirals into the star and vaporises in its hellish fires.</p>
<p>The process of tidal disruption was first suggested some 50 years ago. For the last couple of decades, astronomers — including my group — have observed dozens of bright tidal disruption flares caused by <a href="https://science.nasa.gov/resource/tidal-disruption-event/">stars shredded by supermassive black holes</a> in the centres of galaxies. </p>
<figure class="align-center ">
<img alt="Planet and binary star." src="https://images.theconversation.com/files/583650/original/file-20240322-26-mpjqcm.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/583650/original/file-20240322-26-mpjqcm.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/583650/original/file-20240322-26-mpjqcm.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/583650/original/file-20240322-26-mpjqcm.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/583650/original/file-20240322-26-mpjqcm.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/583650/original/file-20240322-26-mpjqcm.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/583650/original/file-20240322-26-mpjqcm.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">
<figcaption>
<span class="caption">The new study in Nature looked specifically at stars orbiting each other in binary systems.</span>
<span class="attribution"><a class="source" href="https://images.nasa.gov/details/PIA21470">NASA/JPL-Caltech</a></span>
</figcaption>
</figure>
<p>Last year, for the first time, a group of astronomers reported observing a similar, dimmer flare that was consistent with <a href="https://www.nasa.gov/missions/neowise/caught-in-the-act-astronomers-detect-a-star-devouring-a-planet/">a planet being disrupted and consumed by its star</a>. </p>
<p>Tidal disruption of planets may be quite common, as shown by the new finding that at least 1 in 12 stars exhibits signs that <a href="https://www.nature.com/articles/d41586-024-00847-6">they have ingested planetary material</a>. </p>
<p>Other studies have found that between a quarter to half of all white dwarfs – the remnants of stars up to twice as massive as our Sun – sport similar scars. As their name implies, white dwarfs are white hot. With surface temperatures of tens of thousands of degrees, the hottest white dwarfs emit ultraviolet and X-ray light energetic enough to <a href="https://www.syfy.com/syfy-wire/a-dead-star-is-vaporizing-its-planets">vaporise their orbiting planets</a>.</p>
<h2>The end of Earth</h2>
<p>Rest assured; Earth won’t be destroyed via tidal disruption. Our planet’s end will come in about five billion years, when the Sun will transition into a red giant. </p>
<p>Stars are powered by <a href="https://www.energy.gov/science/doe-explainsnuclear-fusion-reactions#:%7E:text=Nuclear%20Fusion%20reactions%20power%20the,The%20leftover%20mass%20becomes%20energy.">the process known as fusion</a>, where two light elements are combined to make a heavier one. All stars start out their lives fusing the element hydrogen in their cores into the element helium. This fusion process both stabilises them against implosion, due to the incessant pull of gravity, and creates the light that makes them shine. Our Sun has been fusing hydrogen into helium for roughly 4.5 billion years. </p>
<p>But 4.5 billion years from now, the hydrogen in the Sun’s core will run out. All fusion in the core will stop, and gravity, unopposed, will force the star to contract. As the core contracts, it will heat up until the temperature is high enough for helium to fuse into carbon. </p>
<p>Fusion will once again stabilise the star. In the meantime, though, the outer envelopes of the star will expand and cool, giving the now giant star a redder hue. As the red giant Sun expands, it will <a href="https://www.scientificamerican.com/article/the-sun-will-eventually-engulf-earth-maybe/">engulf Mercury, Venus and Earth</a> – it may even reach all the way out to the orbit of Mars. </p>
<p>Earth may have another five billion years to go, but we will not be here to witness its extinction. As the Sun burns through its hydrogen stores, it steadily grows brighter: every billion years, its luminosity increases by about 10%. </p>
<p>A billion years from now, the Sun will be bright enough to <a href="https://theconversation.com/the-sun-wont-die-for-5-billion-years-so-why-do-humans-have-only-1-billion-years-left-on-earth-37379">boil away Earth’s oceans</a>. So, the next time you bask in the warm rays of the Sun, remember: it’s got it in for us.</p><img src="https://counter.theconversation.com/content/226361/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Or Graur receives funding from UKRI Science and Technology Facilities Council.. </span></em></p>There are several ways in which stars can destroy and swallow their own planets.Or Graur, Associate Professor of Astrophysics, University of PortsmouthLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2259552024-03-22T12:32:20Z2024-03-22T12:32:20ZAn eclipse for everyone – how visually impaired students can ‘get a feel for’ eclipses<figure><img src="https://images.theconversation.com/files/583493/original/file-20240321-24-k7j1j4.jpg?ixlib=rb-1.1.0&rect=0%2C5%2C1997%2C1398&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A solar eclipse approaching totality. </span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/Total%20Solar%20Eclipse%20Photo%20Gallery/d4f2edfa2e47448980ce303f299063ae?hpSectionId=8053d9e3a7de4b25a8bccd33428f5964&st=hpsection&mediaType=photo&sortBy=arrivaldatetime:desc&dateRange=Anytime&totalCount=3429&currentItemNo=22">AP Photo/Richard Vogel, File</a></span></figcaption></figure><p>Many people in the U.S. will have an opportunity to witness nearly four minutes of a <a href="https://theconversation.com/what-would-a-solar-eclipse-look-like-from-the-moon-an-astronomer-answers-that-and-other-total-eclipse-questions-81308">total solar eclipse</a> on Monday, April 8, 2024, as it moves from southern Texas to Maine. But in the U.S., over 7 million people are <a href="https://nfb.org/blindness-statistics">blind or visually impaired</a> and may not be able to experience an eclipse the traditional way. </p>
<p>Of course they, like those with sight, will feel colder as the Sun’s light is shaded, and will hear the songs and sounds of birds and insects change as the light dims and brightens. But much of an eclipse is visual.</p>
<p>We are a <a href="https://scnasaepscor.charleston.edu/contact-us/">planetary scientist</a> and <a href="https://www.edinboro.edu/academics/schools-and-departments/cshp/departments/geosciences/planetarium/director.php">an astronomer</a> who, with funding and support from NASA’s <a href="https://sservi.nasa.gov/articles/">Solar System Exploration Research Virtual Institute</a>, have created and published a set of <a href="https://sservi.nasa.gov/books/eclipses.html">tactile graphics</a>, or graphics with raised and textured elements, on the 2024 total solar eclipse. </p>
<p>The guide, called “Getting a Feel for Eclipses,” illustrates the paths of the 2017 total, 2023 annular and <a href="https://science.nasa.gov/eclipses/future-eclipses/eclipse-2024/where-when/">2024 total solar eclipses</a>. In a <a href="https://theconversation.com/what-would-a-solar-eclipse-look-like-from-the-moon-an-astronomer-answers-that-and-other-total-eclipse-questions-81308">total eclipse</a>, the Moon fully blocks the Sun from Earth view, while during an <a href="https://www.nesdis.noaa.gov/annular-solar-eclipse">annular eclipse</a>, a narrow ring of sunlight can be seen encircling the Moon. </p>
<p>The tactile graphics and associated online content detail the <a href="https://theconversation.com/solar-eclipses-result-from-a-fantastic-celestial-coincidence-of-scale-and-distance-224113">specific alignment of the Earth, Moon and Sun</a> under which eclipses occur. </p>
<p>To date, we have distributed almost 11,000 copies of this book to schools for the blind, state and local libraries, the Library of Congress and more.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/583257/original/file-20240320-20-10b7nu.jpg?ixlib=rb-1.1.0&rect=25%2C3%2C2085%2C1553&q=45&auto=format&w=1000&fit=clip"><img alt="A map of the US with three curved lines stretching across, indicating the eclipses of 2024, 2023 and 2017." src="https://images.theconversation.com/files/583257/original/file-20240320-20-10b7nu.jpg?ixlib=rb-1.1.0&rect=25%2C3%2C2085%2C1553&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/583257/original/file-20240320-20-10b7nu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=443&fit=crop&dpr=1 600w, https://images.theconversation.com/files/583257/original/file-20240320-20-10b7nu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=443&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/583257/original/file-20240320-20-10b7nu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=443&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/583257/original/file-20240320-20-10b7nu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=556&fit=crop&dpr=1 754w, https://images.theconversation.com/files/583257/original/file-20240320-20-10b7nu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=556&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/583257/original/file-20240320-20-10b7nu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=556&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 Getting A Feel for Eclipses’ guide helps blind and visually impaired people learn about the eclipse.</span>
<span class="attribution"><a class="source" href="https://sservi.nasa.gov/books/eclipses.html">NASA SSERVI</a></span>
</figcaption>
</figure>
<h2>Why publish a tactile book on eclipses?</h2>
<p>NASA has <a href="https://science.nasa.gov/eclipses">lots of explanatory material</a> that helps people visualize and understand rare phenomena like eclipses. But for people with visual impairments, maps and images don’t help. For tactile readers, their sense of touch is their vision. That’s where this guide and our other tactile books come in.</p>
<p>Over <a href="https://nfb.org/blindness-statistics">65,000 students in the U.S.</a> are blind or visually impaired. After working with several of our students who are totally blind, we wanted to find out how to make events like eclipses as powerful for these students as they are for us. We also wanted to help our students visualize and understand the concept of an eclipse. </p>
<p>These aims resulted in the three <a href="https://www.pathstoliteracy.org/tactile-graphics/">tactile graphics</a>, which are physical sheets with textures and raised surfaces that can be interpreted through touch, <a href="https://sservi.nasa.gov/books/eclipses.html">as well as online content</a>. </p>
<p>The first tactile graphic models the <a href="https://theconversation.com/solar-eclipses-result-from-a-fantastic-celestial-coincidence-of-scale-and-distance-224113">alignment of the Earth, Moon and Sun</a>. The second illustrates the phases of an eclipse as the Moon moves in between the Earth and Sun to full totality, and then out of the way. The third includes a map of the continental U.S. that illustrates the paths of three eclipses: the <a href="https://www.weather.gov/pah/TotalSolarEclipse2017">Aug. 21, 2017, total eclipse</a>, the <a href="https://science.nasa.gov/eclipses/future-eclipses/eclipse-2023/where-when/">Oct. 14, 2023, annular eclipse</a> and the <a href="https://science.nasa.gov/eclipses/future-eclipses/eclipse-2024/where-when/">Apr. 8, 2024, total eclipse</a>. We used different textures to illustrate these concepts.</p>
<p>Each book includes a QR code on the front cover, outlined by a raised square boundary. The code links to <a href="https://sservi.nasa.gov/books/eclipses.html">an online guide</a> that leads the user through the content behind the graphics while also providing background information. With the online content, users may opt to print the information in large font or have it read to them by a device.</p>
<p>Although initially created to assist visually impaired audiences, these books are still helpful resources for those with sight. Some students can see but might learn better when able to explore the tactile parts of the guide while listening to the audio. Often it’s helpful for students to get the same information presented in different styles, with options to read or have the content information read to them. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/583490/original/file-20240321-18-camylh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A sheet of paper with raised textures labeled Sun, Umbra, Moon and Totality, with three students touching the textures." src="https://images.theconversation.com/files/583490/original/file-20240321-18-camylh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/583490/original/file-20240321-18-camylh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/583490/original/file-20240321-18-camylh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/583490/original/file-20240321-18-camylh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/583490/original/file-20240321-18-camylh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/583490/original/file-20240321-18-camylh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/583490/original/file-20240321-18-camylh.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"></a>
<figcaption>
<span class="caption">Students at Florida School for the Deaf and Blind in St. Augustine explore tactiles 1 and 2.</span>
<span class="attribution"><span class="source">Florida School for the Deaf and Blind</span></span>
</figcaption>
</figure>
<h2>How are the books made?</h2>
<p>We hand-make each book starting by identifying which science concepts the user will likely want to know, and which illustrations can support those concepts.</p>
<p>Once identified, the next step is to create a tactile master, or model, which has one or more raised textures that help to define the science concepts. We pick a set of unique textures to use on the master to signify different items, so the Sun feels different than the Earth. This way, the textures of the graphics become part of the story being shared. </p>
<p>For example, in a model of the Sun’s surface, we use <a href="https://www.britannica.com/plant/Spanish-moss">Spanish moss</a> to create the dynamic texture of the Sun. In past projects, we’ve used textures like doll hair, sand and differently textured cardboard to illustrate planet features, instruments on spacecraft, fine surface features and more. Then, we add <a href="https://www.afb.org/blindness-and-low-vision/braille/what-braille">Braille labels</a> for figure titles, key features and specific notes.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/583492/original/file-20240321-28-ku4w3n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A circle filled with moss." src="https://images.theconversation.com/files/583492/original/file-20240321-28-ku4w3n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/583492/original/file-20240321-28-ku4w3n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/583492/original/file-20240321-28-ku4w3n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/583492/original/file-20240321-28-ku4w3n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/583492/original/file-20240321-28-ku4w3n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/583492/original/file-20240321-28-ku4w3n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/583492/original/file-20240321-28-ku4w3n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&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 tactile master – Spanish moss – used for the Sun.</span>
<span class="attribution"><span class="source">Cassandra Runyon</span></span>
</figcaption>
</figure>
<p>Once we’ve finished making the masters and laying out each page, a small family print shop – McCarty Printing in Erie, Pennsylvania – prints the page titles and key feature labels on Brailon, a type of plastic paper. </p>
<p>Once printed, we place the masters and the Brailon sheets on a thermoform Machine, which heats up the sheets and creates a vacuum that forms the final tactile graphics. Then, we return the pages to McCarty Printing for binding. </p>
<h2>Viewing and experiencing the eclipse</h2>
<p>Like fully sighted people, people with partial vision should avoid looking directly at the Sun. Instead, everyone should <a href="https://theconversation.com/total-solar-eclipses-while-stunning-can-damage-your-eyes-if-viewed-without-the-right-protection-221381">use eclipse glasses</a>. If you don’t have eclipse glasses, you can use an indirect viewing method such as a <a href="https://science.nasa.gov/eclipses/future-eclipses/eclipse-2024/safety/">colander or pinhole projector</a>.</p>
<p>As the eclipse approaches totality, take time to enjoy your surroundings, feel the changes in temperature and light, and note how the animals around you react to the remarkable event using another of your senses – sound.</p><img src="https://counter.theconversation.com/content/225955/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Cassandra Runyon receives funding from NASA's Office of STEM Engagment through the National Space Grant Program and the Established Program to Stimulate Competitive Research (EPSCoR) as well as NASA's Solar System Exploration Research Virtual Institure (SSERVI). She is the Director of both the NASA South Carolina Space Grant Consortium and NASA South Carolina EPSCoR program and Vice Chair of the National Council of Space Grant Directors.</span></em></p><p class="fine-print"><em><span>David Hurd receives funding from the NSF and NASA SSERVI.</span></em></p>Eclipses are rare, fantastic celestial events. Here’s how educators can help visually impaired students enjoy eclipses alongside their sighted peers.Cassandra Runyon, Professor of Geology & Environmental Geosciences, College of CharlestonDavid Hurd, Professor of Geosciences, Pennsylvania Western UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2259902024-03-20T19:03:17Z2024-03-20T19:03:17ZPlanet cannibalism is common, says cosmic ‘twin study’<figure><img src="https://images.theconversation.com/files/582969/original/file-20240319-20-8o3pjz.jpeg?ixlib=rb-1.1.0&rect=0%2C0%2C2560%2C1912&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Intouchable / Openverse</span></span></figcaption></figure><p>How stable are planetary systems? Will Earth and its seven siblings always continue in their steady celestial paths, or might we one day be randomly ejected from our cosmic home?</p>
<p>Physicists understand the rules that govern the orbits of two celestial bodies, but as soon as a third is added (let alone a fourth, fifth, or hundredth) the dynamics become far more complex. Unpredictable instabilities arise, in which an object may be randomly ejected into space or fall into its host star.</p>
<p>The so-called “three-body problem” has troubled scientists for centuries (and more recently forms the premise of a <a href="https://www.bloomsbury.com/au/threebody-problem-9781035909575/">bestselling series</a> of science fiction novels and a <a href="https://www.netflix.com/au/title/81024821">new Netflix adaptation</a>). One obstacle to understanding it has been that we know relatively little about how common it is for such catastrophic instabilities to arise. </p>
<p>In a new study <a href="https://www.nature.com/articles/s41586-024-07091-y">published in Nature</a>, we and our colleagues have shed some light on this question. In a survey of nearby stars, we found as many as one in dozen pairs of stars may have devoured a planet, likely because the planet developed a “wobble” in its orbit and fell into the star.</p>
<h2>Studying twins</h2>
<p>Our study found at least 8% of pairs of stars in our sample show chemical anomalies indicating one star had engulfed planetary material that once orbited it. </p>
<p>To detect this subtle signal, we had to rule out other possible explanations for these chemical patterns. So we focused on “twin stars”, known to have been born at the same time from the same mix of materials. </p>
<p>This approach can eliminate confounding factors, in the same way that studies of twins are sometimes used in sociological or medical research. </p>
<p>The result comes from a survey of twin stars named <a href="https://academic.oup.com/mnras/article/526/2/2181/7287617">C3PO</a> which one of the authors (Ting) initiated in the US, and Liu and others later joined. </p>
<p>Our team collected an exquisite sample of spectroscopic data from 91 pairs of twin stars – many times larger than similar studies conducted in the past. </p>
<p>We found that some stars differed from their twins, showing a distinct chemical pattern with higher amounts of certain elements like iron, nickel and titanium compared to others such as carbon and oxygen. These differences indicate strong evidence that the star has ingested a planet.</p>
<h2>Instabilities may be unexpectedly common</h2>
<p>If a host star engulfs one or more members of a planetary system, it suggests some instability in the dynamics of the system must have occurred. </p>
<p>Simulations suggest such instability may be common in the early life of a planetary system – the first 100 million years or so. However, any traces of planets engulfed during this early period would be undetectable in the stars we observed which are billions of years old.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/new-evidence-for-an-unexpected-player-in-earths-multimillion-year-climate-cycles-the-planet-mars-225454">New evidence for an unexpected player in Earth’s multimillion-year climate cycles: the planet Mars</a>
</strong>
</em>
</p>
<hr>
<p>This suggests the chemical anomalies we saw were caused by more recent instabilities, causing the stars to consume some planets or planetary material. </p>
<p>This revelation is not entirely unexpected. Theorists who study planetary dynamics, including our co-author Bertram Bitsch, have noted that many planetary systems are known to be unstable, especially among systems with a kind of planet called a “super-Earth” – somewhat larger planets than Earth but far smaller than giants like Jupiter.</p>
<p>Systems including a super-Earth planet may be particularly unstable. The gravitational tug-of-war between the host star and its massive planets might generate instability.</p>
<h2>A delicate balance</h2>
<p>Our study encourages us to reconsider our place in the universe. While we take stability for granted in our Solar System, this may not be normal throughout the cosmos. </p>
<p>Our study does not suggest we are likely to see such instabilities in our own Solar System. Even with our new results, however, it is important to recognise that planet engulfment and instability still occur only in a minority of cases.</p>
<p>We hope our study will inspire more people to study planetary systems and their relationship with their host stars. Our understanding of the dynamics of multiple-body systems is still very much incomplete.</p>
<p>As we continue to explore the mysteries of the cosmos, studies like this remind us of the delicate balance that allows life to thrive on Earth and the potential fragility of our cosmic home.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-three-body-problem-liu-cixins-extraterrestrial-novel-is-a-heady-blend-of-politics-ethics-physics-and-chinese-history-218793">The Three-Body Problem: Liu Cixin's extraterrestrial novel is a heady blend of politics, ethics, physics and Chinese history</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/225990/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 largest study yet of ‘twin stars’ shows planetary orbits may be less stable than we thought.Yuan-Sen Ting, Associate Professor, Astrophysics, Australian National UniversityFan Liu, Research Fellow, School of Physics and Astronomy, Monash UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2259062024-03-20T17:15:37Z2024-03-20T17:15:37ZHow a balloon-borne experiment can do the job of the Hubble space telescope<figure><img src="https://images.theconversation.com/files/583085/original/file-20240320-20-8uzvny.jpg?ixlib=rb-1.1.0&rect=45%2C34%2C3788%2C2121&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">SuperBIT waiting for launch while its giant helium balloon is inflated.</span> <span class="attribution"><span class="source">Bill Rodman/NASA</span></span></figcaption></figure><p>An astronomical telescope designed to complement the ageing <a href="https://esahubble.org/">Hubble Space Telescope</a> lifted off from New Zealand’s south island on April 16 2023. But as a sphere the size of a football stadium rose silently and slowly over the Tauhinukorokio mountains, calls started coming in from residents. </p>
<p>Local police and radio stations, however, had been briefed by Nasa that the giant helium balloon would lift the two-ton <a href="https://sites.physics.utoronto.ca/bit">SuperBIT</a> telescope to 40km above sea level, over the next three hours. The mission, in which we were involved, was to test whether a balloon-borne telescope could capture <a href="https://blogs.nasa.gov/superpressureballoon/category/2023-campaign/superbit/">deep space images</a> with high enough resolution to study the unknown substance, dubbed <a href="https://www.esa.int/Science_Exploration/Space_Science/What_are_dark_matter_and_dark_energy">dark matter</a>, that is 85% of all material in the universe.</p>
<p>The observations and subsequent data analysis have proved that balloon-borne experiments can be just as useful as those launched by rockets, but are much cheaper. It is now up to scientists, government agencies and private companies to make the most of them.</p>
<p>For the next month, <a href="https://earth.nullschool.net/#2023/05/01/2300Z/wind/isobaric/10hPa/orthographic=-213.50,-71.03,550">polar stratospheric winds</a> carried SuperBIT <a href="https://www.csbf.nasa.gov/map/balloon10/Google728NT.htm">around the world every eight days</a>, mainly over the Antarctic ocean but clipping the tip of South America. It went where the wind carried it, but could look in any direction. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/582186/original/file-20240315-24-1009uq.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Flight path of SuperBIT, five and a half times around the Southern ocean." src="https://images.theconversation.com/files/582186/original/file-20240315-24-1009uq.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/582186/original/file-20240315-24-1009uq.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/582186/original/file-20240315-24-1009uq.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/582186/original/file-20240315-24-1009uq.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/582186/original/file-20240315-24-1009uq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/582186/original/file-20240315-24-1009uq.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/582186/original/file-20240315-24-1009uq.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">Flight path of SuperBIT.</span>
<span class="attribution"><span class="source">Nasa</span></span>
</figcaption>
</figure>
<p>Each day, solar panels recharged its batteries. At night, it photographed the sky, including the <a href="https://apod.nasa.gov/apod/ap230427.html">Tarantula nebula</a>, a light source 160,000 light years away, and clusters of galaxies 20,000 times farther. </p>
<p>Without a tripod, SuperBIT used gyroscopes to stabilise any swinging (we discovered that the stratosphere is remarkably calm … except in turbulence above the Andes, where SuperBIT once dropped 1,000 feet). It was the first balloon-borne telescope to achieve <a href="https://pubs.aip.org/aip/rsi/article/91/3/034501/1032358/Robust-diffraction-limited-near-infrared-to-near">Hubble-like performance</a> for the short wavelengths of light that are visible to a human eye.</p>
<p>The balloon and the telescope continued to work perfectly, but satellite communication links gradually failed. We think radiation damaged SuperBIT’s <a href="https://www.starlink.com">antennae</a>. We could still download data by <a href="https://www.mdpi.com/2226-4310/10/11/960">dropping hard drives</a>, attached to the telescope, to the ground. But ultimately, Nasa wanted their balloon back, so we brought the telescope down by parachute to Argentina. </p>
<p>This was SuperBIT’s <a href="https://arxiv.org/abs/1807.02887">fifth flight</a>, building on ten years of graft. </p>
<h2>Balloon benefits</h2>
<p>Unlike orbital missions, if balloon payloads don’t work first time, they can be fixed and relaunched. This fosters simple, creative design. Components now proven to <a href="https://www.nasa.gov/directorates/somd/space-communications-navigation-program/technology-readiness-levels/">work in space</a> include hair gel (to hold things), chicken roasting bags (to keep them warm), and parts of bows used by Olympic archers (to let them go).</p>
<p>Failure and success are both opportunities to learn. After each flight, we make-do-and-mend, or improve the technology. For example, since cameras have rapidly got better and cheaper, we have fitted SuperBIT with a new sensor each year. All this reduces costs.</p>
<p>Most of the cost of traditional spaceflight is to mitigate the risk of failure. Compromises are always needed between safety, protecting expensive equipment and getting data. </p>
<p>If a balloon mission goes wrong, it usually matters less, because we get the equipment back. SuperBIT was built mainly by <a href="https://sites.physics.utoronto.ca/barthnetterfield">Canadian PhD students</a>, who have already spun-out a new <a href="https://www.starspectechnologies.com">tech company</a>.</p>
<p>Risk management is different for balloons, and Nasa doesn’t always get the balance right. Waiting for “perfect” weather and the perfectly designed balloon <a href="https://ntrs.nasa.gov/api/citations/20210017816/downloads/2021%20Balloon%20Technology%20Presentation%20-%20Overview%20of%20the%20NASA%20Scientific%20Balloon%20Activities%20-%20Fairbrother.pptx.pdf">grounded all launches from Texas in 2017</a>. Physically impossible calculations of risk, such as a balloon bursting three times, nearly tanked the 2023 programme. </p>
<p>A balloon can only burst once. But <a href="https://cnes.fr/en">France’s</a> and <a href="https://www.asc-csa.gc.ca/eng">Canada’s</a> space agencies, the US <a href="https://ncar.ucar.edu/">National Center for Atmospheric Research</a> and the UK Science Research Council have all proved that a balloon can be relaunched every few days. Risk assessment can be more realistic. Balloon teams can continually test, play around with and improve the process. For rocket launches, there is one chance only.</p>
<h2>Growing international interest</h2>
<p>Geography is important in developing a successful national balloon programme. Countries with expansive landmass can carry out short flights within their own airspace, such as Canada and the US. Northern European countries can use <a href="https://earth.nullschool.net/#2023/07/02/1500Z/wind/isobaric/10hPa/orthographic=-52.92,30.22,533">stable and reliable summer winds</a> to extend flights across the Atlantic ocean, for example from Scotland to Canada.</p>
<p>Countries can also launch from the territory of partner nations around the world, such as the UK <a href="https://www.gov.uk/government/news/space-bridge-across-the-world-will-help-uk-and-australia-get-ahead-in-global-space-race">launching from Australia</a>. </p>
<p>Geopolitics also influences the choice of flight path: a lesson well learned from the <a href="https://www.bbc.co.uk/news/world-us-canada-66062562">rogue Chinese balloon</a> that flew over the US in 2023 and was ultimately shot down. Crossing any country’s airspace requires permission, and we avoid war zones or areas of conflict where the balloon could be mistaken for a hostile target. This is one reason we launched from New Zealand.</p>
<figure class="align-center ">
<img alt="SuperBIT held by a crane for final checks." src="https://images.theconversation.com/files/582942/original/file-20240319-28-a2dkvq.jpeg?ixlib=rb-1.1.0&rect=217%2C0%2C3814%2C2933&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/582942/original/file-20240319-28-a2dkvq.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/582942/original/file-20240319-28-a2dkvq.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/582942/original/file-20240319-28-a2dkvq.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/582942/original/file-20240319-28-a2dkvq.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/582942/original/file-20240319-28-a2dkvq.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/582942/original/file-20240319-28-a2dkvq.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">
<figcaption>
<span class="caption">SuperBIT held by a crane for final checks.</span>
<span class="attribution"><span class="source">Richard Massey</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Government interest in national balloon programmes is increasing, as new material science and manufacturing techniques have created balloons that retain helium, lengthening flights from days to months. The US reaffirmed their interest in a <a href="https://www.whitehouse.gov/briefing-room/statements-releases/2023/12/20/fact-sheet-strengthening-u-s-international-space-partnerships/">2023 government paper</a> and <a href="https://www.asc-csa.gc.ca/eng/sciences/balloons/about-stratospheric-balloons.asp">Canada</a>, <a href="https://cnes.fr/en/how-stratospheric-balloons-work%20and%20https://www.hemera-h2020.eu/facilities-2/cnes-balloons/">France</a> and <a href="https://sscspace.com/esrange/">Sweden</a> have long-established balloon programmes. </p>
<p>The UK ran a world-leading balloon programme until the 1990s. Abandoning it lost an opportunity to train scientists and engineers into leadership roles. British teams are still often invited to join French or US satellite missions, but we no longer lead or decide what gets built. We foresee few technical, geographic or political barriers to the UK restarting a balloon programme in parallel to its nascent rocket launches.</p>
<h2>Balloons are high enough</h2>
<p>Officially, space begins 100km above sea level. But there is no magic line, and <a href="https://iopscience.iop.org/article/10.3847/1538-3881/abbffb">precious little atmosphere above 40km</a>. There, stars stop twinkling and the sky is black. Long exposure astronomical photographs become pin sharp and reveal faint, distant objects that are blurred to astronomers on the ground.</p>
<figure class="align-center ">
<img alt="SuperBIT shrouded in early-morning mist before launch." src="https://images.theconversation.com/files/582920/original/file-20240319-28-8sm5fb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/582920/original/file-20240319-28-8sm5fb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/582920/original/file-20240319-28-8sm5fb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/582920/original/file-20240319-28-8sm5fb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/582920/original/file-20240319-28-8sm5fb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/582920/original/file-20240319-28-8sm5fb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/582920/original/file-20240319-28-8sm5fb.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">SuperBIT shrouded in early-morning mist before launch.</span>
<span class="attribution"><span class="source">Steven Benton</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Balloon cameras or spectrographs can also look down, and are high enough to capture Earth observations just like those from satellites. They can also take atmospheric measurements around them, including of the ozone layer in the stratosphere.</p>
<p>Balloons won’t replace all rockets, as they can’t travel higher than 40km.
And even though helium is a <a href="https://www.npr.org/2019/11/01/775554343/the-world-is-constantly-running-out-of-helium-heres-why-it-matters">finite resource</a>, balloons are more “environmentally-friendly”. They require no rocket fuels during launch, don’t add to increasing space debris in orbit – and at the end of their working life, they aren’t <a href="https://theconversation.com/satellites-are-burning-up-in-the-upper-atmosphere-and-we-still-dont-know-what-impact-this-will-have-on-the-earths-climate-223618">burnt up in the atmosphere</a>. What’s not to like?</p><img src="https://counter.theconversation.com/content/225906/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Richard Massey has received funding for SuperBIT from the Royal Society and from UKRI's Science and Technology Facilities Council. </span></em></p><p class="fine-print"><em><span>Fionagh Thomson has carried out consultancy work for the UK space agency. She is an elected member of the sustainability committees for the Royal Astronomical Society and the European Astronomical society.</span></em></p>Giant helium balloons are a cheap, more environmentally friendly alternative to rocket launches – and you get the satellite back.Richard Massey, Professor of extragalactic astrophysics (dark matter and cosmology), Durham UniversityFionagh Thomson, Senior Research Fellow in Disruptive Technologies, Space/Environmental Ethics, Visual ethnographer, Durham UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2255022024-03-18T18:09:02Z2024-03-18T18:09:02ZFloating crystals slow stellar aging — for some stars, this can delay death by billions of years<p>Imagine the embers of a campfire, slowly dimming over time. That is the fate most stars in the universe face. After their nuclear fuel is spent, 98 per cent of stars — including our sun — will eventually become white dwarfs. These small, dense remnants are thought to <a href="https://esahubble.org/wordbank/white-dwarf/">simply cool down</a>, becoming ever fainter as the universe ages.</p>
<p>In 2019, astronomers discovered <a href="https://doi.org/10.3847/1538-4357/ab4989">a group of white dwarfs</a> that mysteriously stopped cooling. These “forever-young” stars remain at a near-constant surface temperature for at least eight billion years — an incredible length of time, considering the universe is <a href="https://www.space.com/24054-how-old-is-the-universe.html">13.8 billion years old</a>. </p>
<p>Something is fuelling these stars from within, but given that they had run out of their nuclear fuel source, scientists were unsure what could be keeping them shining so brightly. Our research, <a href="https://doi.org/10.1038/s41586-024-07102-y">recently published in <em>Nature</em></a>, presents the solution to this conundrum.</p>
<p>Using information gathered by the <a href="https://www.esa.int/Science_Exploration/Space_Science/Gaia">Gaia space observatory of the European Space Agency</a>, researchers discovered that some white dwarfs essentially stop cooling.</p>
<p>By studying how white dwarfs are distributed as a function of temperature (from hot to cold) <a href="https://sci.esa.int/web/gaia/-/61343-shedding-light-on-white-dwarfs-the-future-of-stars-like-our-sun">in the Gaia data</a>, astronomers noticed an accumulation of white dwarfs at intermediate temperatures. This indicates that some white dwarfs spend more time at these intermediate temperatures — eight billion years more than thought possible.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/nkXR7bpmy7Q?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Interview with University of Victoria astrophysics researcher Simon Blouin.</span></figcaption>
</figure>
<h2>Stellar crystals</h2>
<p>White dwarfs are weird. A mere teaspoon of material from their cores <a href="https://astronomy.swin.edu.au/cosmos/W/white+dwarf">weighs several tonnes</a>. Under such extreme densities, matter can behave strangely. Even though the interiors of white dwarfs are millions of degrees hot, the density is high enough that they can freeze into a solid state. They form crystals out of the carbon, oxygen and other elements present in their interiors.</p>
<p>The formation of these crystals normally starts at the centre of the star, where density is highest. As the white dwarf cools down, more crystals are formed in successive layers until almost the whole star is completely solid.</p>
<p>However, this inside-out crystallization does not apply to all white dwarfs. We discovered that the heaviest elements present in white dwarfs are expelled from the crystals as they are formed, just as <a href="https://nsidc.org/learn/parts-cryosphere/sea-ice/science-sea-ice">salt is expelled from ice crystals</a> when seawater freezes.</p>
<p>The crystals become less dense than their surroundings, and float up like ice cubes in a glass of water. As the crystals do not stay in place, the core cannot simply freeze from the inside out.</p>
<p>The movements created by the floating crystals reshuffle the chemical layering inside the star. Gradually, the heaviest elements are transported toward the centre. This releases a steady flow of gravitational energy that keeps the star shining at a near-constant temperature for billions of years.</p>
<p>Floating crystals can pause the stellar aging process, providing a final energy source to otherwise dead stars.</p>
<h2>The exception or the rule?</h2>
<p>So far, this cooling pause has been conclusively identified only for a small fraction of the white dwarf population. The high masses and peculiar compositions of these anomalous white dwarfs suggest that they had quite violent histories. Most likely, they are the products of stellar mergers — events where two stars collide and combine.</p>
<p>But this may be just the tip of the iceberg. Based on our findings, we suspect that almost all white dwarfs, and not just the merged ones, experience some cooling pause during their evolution. However, this more universal cooling pause would be much shorter than the multi-billion-year interruption studied so far.</p>
<p><a href="https://doi.org/10.1093/mnras/stad1719">Observations are ongoing</a> to try to identify this shorter cooling pause in the rest of the white dwarf population.</p>
<h2>Cosmic clocks</h2>
<p>These findings have implications for stellar archaeology. The cooler the white dwarf, the older it must be. Just as archeologists use carbon-14 dating to determine the age of artifacts and reconstruct the history of a city or civilization, astronomers rely on white dwarf cooling to measure the ages of stars and understand the history of our Milky Way galaxy.</p>
<p>Our discovery makes this more complicated. A white dwarf with a certain temperature could be billions of years older than initially assumed because of the formation of these floating crystals. The key now is to figure out which stars experience this cooling pause and which do not.</p><img src="https://counter.theconversation.com/content/225502/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Simon Blouin receives funding from the Natural Sciences and Engineering Research Council of Canada. </span></em></p>Floating crystals can pause the stellar aging process, providing a final energy source to otherwise dead stars.Simon Blouin, CITA National Postdoctoral Fellow, Astrophysics, University of VictoriaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2227072024-03-13T19:13:22Z2024-03-13T19:13:22ZTotal solar eclipses provide an opportunity to engage with science, culture and history<figure><img src="https://images.theconversation.com/files/580943/original/file-20240311-16-li8vda.jpg?ixlib=rb-1.1.0&rect=0%2C5%2C3724%2C2146&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Throughout time, eclipses have inspired societies to understand the cosmos and its events.</span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><p>On April 8, 2024, there will be a total solar eclipse in Canada. This is an opportunity to experience, learn from and participate in the excitement and wonder. And rather than hiding inside, researchers have been communicating how people can safely enjoy this unique opportunity.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/on-april-8-2024-parts-of-ontario-quebec-the-maritimes-and-newfoundland-will-see-a-total-eclipse-of-the-sun-heres-how-to-get-ready-for-it-203382">On April 8, 2024, parts of Ontario, Québec, the Maritimes and Newfoundland will see a total eclipse of the sun. Here's how to get ready for it.</a>
</strong>
</em>
</p>
<hr>
<p>Roughly every 18 months, the sun, moon and Earth come into perfect alignment and somewhere on Earth <a href="https://eclipse.gsfc.nasa.gov/SEatlas/SEatlas.html">experiences a solar eclipse</a>. During this phenomenon, the moon casts a roughly 250 km wide shadow onto Earth.</p>
<p>This ephemeral daytime darkness can be a once-in-a-lifetime experience. The last time Toronto experienced a total solar eclipse was on <a href="http://xjubier.free.fr/en/site_pages/solar_eclipses/xSE_GoogleMap3.php?Ecl=+19250124&Acc=2&Umb=1&Lmt=1&Mag=0&Lat=43.69660&Lng=-79.41391&Elv=162.0&Zoom=8&LC=1">Jan. 24, 1925</a>; the next total solar eclipse will occur in 120 years, on <a href="http://xjubier.free.fr/en/site_pages/solar_eclipses/xSE_GoogleMap3.php?Ecl=+21441026&Acc=2&Umb=1&Lmt=1&Mag=0&Lat=43.69629&Lng=-79.29982&Elv=127.0&Zoom=8&LC=1">Oct. 26, 2144</a>.</p>
<p>Our interpretation of, and response to, total solar eclipses has advanced enormously. Eclipses were once considered cosmic omens that predicted dying kings, good harvests or the need for new territorial treaties. Today, they provide a unique opportunity to consider the physical nature of the universe, and the cosmic privilege of witnessing the alignment of the moon and sun. </p>
<h2>Eclipses and knowledge creation</h2>
<p>Due to their sudden darkness, solar eclipses have been perceived <a href="https://www.cnn.com/2017/07/25/us/history-solar-eclipse/index.html">through history as catastrophic events</a>. Many societies developed stories to <a href="https://www.britannica.com/list/the-sun-was-eaten-6-ways-cultures-have-explained-eclipses">explain these unusual events</a>, often filled with fear and violence. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/580949/original/file-20240311-26-98odlu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="an illustration of a golden brown demon eating a yellow disc against a purple background" src="https://images.theconversation.com/files/580949/original/file-20240311-26-98odlu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/580949/original/file-20240311-26-98odlu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=451&fit=crop&dpr=1 600w, https://images.theconversation.com/files/580949/original/file-20240311-26-98odlu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=451&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/580949/original/file-20240311-26-98odlu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=451&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/580949/original/file-20240311-26-98odlu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=567&fit=crop&dpr=1 754w, https://images.theconversation.com/files/580949/original/file-20240311-26-98odlu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=567&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/580949/original/file-20240311-26-98odlu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=567&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 mural of the Hindu demon Rahu swallowing the moon at the temple Wat Phang La in southern Thailand.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/anandajoti/10684670235/">(Anandajoti Bhikkhu/flickr)</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Indian myths tell of an <a href="https://www.washingtonpost.com/graphics/2017/lifestyle/eclipse-myths/">immortal demon seeking revenge on Vishnu by trying to eat the sun and moon</a>. The Pomo, Indigenous people of Northern California, describe <a href="https://www.exploratorium.edu/eclipse/eclipse-stories-from-around-the-world">a huge angry bear trying to eat the sun</a>. In other mythologies, eclipses were thought to be heavenly forces removing our source of warmth and life.</p>
<p>Beliefs about eclipses motivated ancient Greek astronomers to create the <a href="https://doi.org/10.1371/journal.pone.0103275">antikythera mechanism</a>, a complex analog computer that predicted the timing of future eclipses with a precision of 30 minutes. These predictions were critical for Greek society as a solar eclipse could mean an upcoming death of the king, requiring the appointment of a pseudo-emperor to be killed instead.</p>
<p>Our reactions to eclipses have evolved, driving us to better understand the solar system and the universe at large. </p>
<p>During the eclipse on Aug. 18, 1868, astronomers Norman Lockyer and Pierre Janssen each studied the light from the solar corona to <a href="https://doi.org/10.1007/978-1-4614-5363-5">discover a new chemical element</a>. This chemical element was named helium, after the Greek word for the sun. </p>
<p>On May 29, 1919, Frank Watson Dyson and Arthur Stanley Eddington studied the <a href="https://doi.org/10.1098/rsta.1920.0009">bent path of starlight</a> during a total solar eclipse for the first experimental “<a href="https://timesmachine.nytimes.com/timesmachine/1919/11/10/118180487.pdf">triumph of Einstein’s theory</a>” of general relativity.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/580945/original/file-20240311-20-25sylo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="ancient greenish square fragments" src="https://images.theconversation.com/files/580945/original/file-20240311-20-25sylo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/580945/original/file-20240311-20-25sylo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/580945/original/file-20240311-20-25sylo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/580945/original/file-20240311-20-25sylo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/580945/original/file-20240311-20-25sylo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/580945/original/file-20240311-20-25sylo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/580945/original/file-20240311-20-25sylo.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"></a>
<figcaption>
<span class="caption">Fragments of an antikythera mechanism on display at a museum in Athens, Greece.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<h2>Eclipse experiences</h2>
<p>Unlike many other cosmic events, such as meteor showers or comets, which require expensive telescopes or <a href="https://darksky.org/what-we-do/international-dark-sky-places/">dark sky places</a>, eclipses are a barrier-free celestial event. To safely enjoy the eclipse, one simply needs eclipse viewing glasses or <a href="https://www.jpl.nasa.gov/edu/learn/project/how-to-make-a-pinhole-camera/">a cardboard box</a>. </p>
<p>Many universities across Canada are using the opportunity of the total solar eclipse to engage with people to safely experience this astronomical phenomenon. For example, Queen’s University in Kingston, Canada is making <a href="https://www.queensu.ca/physics/2024-total-solar-eclipse/eclipse-glasses">120,000 eclipse glasses available</a> to make safe eclipse viewing possible for anyone.</p>
<p>In the spirit of education, hundreds of <a href="https://astrosociety.org/education-outreach/amateur-astronomers/eclipse-ambassadors/program.html">eclipse ambassadors</a> are heading to schools to engage with students about having a profound and safe experience during the eclipse. These ambassadors lead workshops on building inexpensive pinhole cameras to project the sun during the eclipse, explaining unique features that can be seen during eclipses, such as <a href="https://science.nasa.gov/resource/baileys-beads/">Bailey’s beads</a> and the <a href="https://www.nasa.gov/image-article/diamond-ring-effect/">diamond ring effect</a>, and helping everyone appreciate the vastness of the solar system.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/580952/original/file-20240311-20-8t2snr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="a black circle surrounded with a ring of light that is thicker in the lower righthand quadrant" src="https://images.theconversation.com/files/580952/original/file-20240311-20-8t2snr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/580952/original/file-20240311-20-8t2snr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=389&fit=crop&dpr=1 600w, https://images.theconversation.com/files/580952/original/file-20240311-20-8t2snr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=389&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/580952/original/file-20240311-20-8t2snr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=389&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/580952/original/file-20240311-20-8t2snr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=489&fit=crop&dpr=1 754w, https://images.theconversation.com/files/580952/original/file-20240311-20-8t2snr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=489&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/580952/original/file-20240311-20-8t2snr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=489&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 Baily’s Beads effect occurs when gaps in the moon’s rugged terrain allow sunlight to pass through in some places just before the total phase of the eclipse.</span>
<span class="attribution"><a class="source" href="https://science.nasa.gov/resource/baileys-beads/">(Aubrey Gemignani/NASA)</a></span>
</figcaption>
</figure>
<p>These efforts demonstrate the universal value of science, and promote science engagement beyond classrooms and institutions.</p>
<p>Not only is the upcoming eclipse being leveraged as an opportunity to inspire the next generation of scientists, but it is also being used for the advancement of scientific knowledge. Unlike the experiments of Dyson, Eddington and Lockyer that were limited to the academy, today’s institutions are mobilizing the public to conduct citizen science experiments. </p>
<p>Initiated by NASA, the <a href="https://eclipsemegamovie.org/goals">Eclipse Megamovie project</a> will use photos taken during totality of the solar eclipse to study the solar corona. In 2017, photos collected during the total eclipse helped researchers identify a plasma plume in the solar corona. The 2024 eclipse will help researchers study this plume in greater detail. </p>
<p>Anyone with a DSLR camera and a tripod can submit a picture of the total solar eclipse to the Eclipse Megamovie project. The public data collected for the 2024 eclipse will far exceed what could be accomplished by any one experiment or location.</p>
<p>April’s total solar eclipse, and others to come, will remind people that science is exciting and inspiring, and that scientific expertise is of profound universal value. Such a celestial coincidence is an opportunity to engage with local communities and discuss the origin and mechanics of our solar system, all while including the public in scientific discovery through crowd-sourcing images of their experience. </p>
<p>All that’s left is to hope for clear skies and marvel once more at the cosmos.</p><img src="https://counter.theconversation.com/content/222707/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nikhil Arora receives funding from the National Sciences and Engineering Research Council of Canada.</span></em></p><p class="fine-print"><em><span>Mark Richardson is based at the Arthur B. McDonald Canadian Astroparticle Physics Research Institute, who has received funding from the Canada First Research Excellence Fund. </span></em></p>Eclipses have inspired myths, predictions and scientific discoveries. The total solar eclipse occurring on April 8 provides a once-in-a-lifetime opportunity to engage with science and the cosmos.Nikhil Arora, Postdoctoral fellow, Physics, Engineering Physics & Astronomy, Queen's University, OntarioMark Richardson, Manager for Education and Public Outreach, Adjunct Professor of Physics and Astronomy, Queen's University, OntarioLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2254542024-03-12T19:14:54Z2024-03-12T19:14:54ZNew evidence for an unexpected player in Earth’s multimillion-year climate cycles: the planet Mars<figure><img src="https://images.theconversation.com/files/580914/original/file-20240311-30-ef6q0e.JPG?ixlib=rb-1.1.0&rect=0%2C8%2C6000%2C3979&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Dietmar Muller</span></span></figcaption></figure><p>Our existence is governed by natural cycles, from the daily rhythms of sleeping and eating, to longer patterns such as the turn of the seasons and the quadrennial round of <a href="https://theconversation.com/leap-of-imagination-how-february-29-reminds-us-of-our-mysterious-relationship-with-time-and-space-224503">leap years</a>. </p>
<p>After looking at seabed sediment stretching back 65 million years, we have found a previously undetected cycle to add to the list: an ebb and flow in deep sea currents, tied to a 2.4-million-year swell of global warming and cooling driven by a gravitational tug of war between Earth and Mars. Our research is <a href="https://doi.org/10.1038/s41467-024-46171-5">published in Nature Communications</a>.</p>
<h2>Milankovitch cycles and ice ages</h2>
<p>Most of the natural cycles we know are determined one way or another by Earth’s movement around the Sun. </p>
<p>As the German astronomer <a href="https://www.jpl.nasa.gov/news/the-history-of-johannes-kepler">Johannes Kepler</a> first realised four centuries ago, the orbits of Earth and the other planets are not quite circular, but rather slightly squashed ellipses. And over time, the gravitational jostling of the planets changes the shape of these orbits in a predictable pattern.</p>
<p>These alterations affect our long-term climate, influencing the coming and going of ice ages. In 1941, Serbian astrophysicist <a href="https://www.amnh.org/learn-teach/curriculum-collections/earth-inside-and-out/milutin-milankovitch-seeking-the-cause-of-the-ice-ages">Milutin Milankovitch</a> recognised that changes in the shape of Earth’s orbit, the tilt of its axis, and the wobbling of its poles all affect the amount of sunlight we receive. </p>
<p>Known as “<a href="https://www.nature.com/scitable/knowledge/library/milankovitch-cycles-paleoclimatic-change-and-hominin-evolution-68244581/">Milankovitch cycles</a>”, these patterns occur with periods of 405,000, 100,000, 41,000 and 23,000 years. Geologists have found traces of them throughout Earth’s deep past, even in <a href="https://www.nature.com/scitable/knowledge/library/milankovitch-cycles-paleoclimatic-change-and-hominin-evolution-68244581/">2.5-billion-year old rocks</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/580915/original/file-20240311-17800-u3fw0j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A photo shows rocky pillars and cliffs in the ocean." src="https://images.theconversation.com/files/580915/original/file-20240311-17800-u3fw0j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/580915/original/file-20240311-17800-u3fw0j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/580915/original/file-20240311-17800-u3fw0j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/580915/original/file-20240311-17800-u3fw0j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/580915/original/file-20240311-17800-u3fw0j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/580915/original/file-20240311-17800-u3fw0j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/580915/original/file-20240311-17800-u3fw0j.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"></a>
<figcaption>
<span class="caption">Fine layering in the Port Campbell Limestone by the Great Ocean Road in Victoria is the product of Earth’s orbital eccentricity and obliquity.</span>
<span class="attribution"><span class="source">Adriana Dutkiewicz</span></span>
</figcaption>
</figure>
<h2>Earth and Mars</h2>
<p>There are also slower rhythms, called astronomical “grand cycles”, which cause fluctuations over millions of years. One such cycle, related to the slow rotation of the orbits of Earth and Mars, recurs every 2.4 million years. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/580907/original/file-20240311-22-m3lfms.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Diagram showing the orbits of Earth and Mars around the Sun." src="https://images.theconversation.com/files/580907/original/file-20240311-22-m3lfms.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/580907/original/file-20240311-22-m3lfms.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/580907/original/file-20240311-22-m3lfms.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/580907/original/file-20240311-22-m3lfms.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/580907/original/file-20240311-22-m3lfms.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/580907/original/file-20240311-22-m3lfms.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/580907/original/file-20240311-22-m3lfms.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">The orbits of Earth and Mars exert a subtle influence on each other in a cycle that repeats every 2.4 million years.</span>
<span class="attribution"><span class="source">NASA</span></span>
</figcaption>
</figure>
<p>The cycle is predicted by <a href="https://www.aanda.org/articles/aa/full_html/2011/08/aa16836-11/aa16836-11.html">astronomical models</a>, but is <a href="https://www.pnas.org/doi/10.1073/pnas.1714342115">rarely detected</a> in geological records. The easiest way to find it would be in sediment samples that continuously cover a period of many millions of years, but these are rare.</p>
<p>Much like the shorter Milankovitch cycles, this grand cycle affects the amount of sunlight Earth receives and has an impact on climate. </p>
<h2>Gaps in the record</h2>
<p>When we went hunting for signs of these multimillion-year climate cycles in the rock record, we used a “big data” approach. <a href="https://www.iodp.org/about-iodp/history">Scientific ocean drilling</a> data collected since the 1960s have generated a treasure trove of information on deep-sea sediments through time across the global ocean. </p>
<p>In our study, published in <a href="https://doi.org/10.1038/s41467-024-46171-5">Nature Communications</a>, we used sedimentary sequences from more than 200 drill sites to discover a previously unknown connection between the changing orbits of Earth and Mars, past global warming cycles, and the speeding up of deep-ocean currents. </p>
<p>Most studies focus on complete, high-resolution records to detect climate cycles. Instead, we concentrated on the parts of the sedimentary record that are missing — breaks in sedimentation called hiatuses. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-plate-tectonics-mountains-and-deep-sea-sediments-have-maintained-earths-goldilocks-climate-183725">How plate tectonics, mountains and deep-sea sediments have maintained Earth's 'Goldilocks' climate</a>
</strong>
</em>
</p>
<hr>
<p>A deep-sea hiatus indicates the action of vigorous bottom currents that eroded seafloor sediment. In contrast, continuous sediment accumulation indicates calmer conditions. </p>
<p>Analysing the timing of hiatus periods across the global ocean, we identified hiatus cycles over the past 65 million years. The results show that the vigour of deep-sea currents waxes and wanes in 2.4 million year cycles coinciding with changes in the shape of Earth’s orbit.</p>
<p>Astronomical models suggest the interaction of Earth and Mars drives a 2.4 million year cycle of more sunlight and warmer climate alternating with less sunlight and cooler climate. The warmer periods correlate with more deep-sea hiatuses, related to more vigorous deep-ocean currents. </p>
<h2>Warming and deep currents</h2>
<p>Our results fit with recent <a href="https://www.nature.com/articles/s41558-021-01006-9">satellite data</a> and <a href="https://www.nature.com/articles/s41558-021-01212-5">ocean models</a> mapping short-term ocean circulation changes. Some of these suggest that ocean mixing has become more intense over the last decades of global warming. </p>
<p>Deep-ocean <a href="https://www.gfdl.noaa.gov/ocean-mesoscale-eddies/">eddies</a> are predicted to intensify in a warming, more energetic climate system, particularly at <a href="https://www.nature.com/articles/s41558-023-01908-w#:%7E:text=Satellite%20altimetry%20records%20reveal%20that,from%201993%20to%2020209">high latitudes</a>, as major storms become more frequent. This makes deep ocean mixing more vigorous. </p>
<p>Deep-ocean eddies are like giant wind-driven whirlpools and often reach the deep sea floor. They result in seafloor erosion and large sediment accumulations called <a href="https://www.sciencedirect.com/science/article/pii/S0070457108100140">contourite drifts</a>, akin to snowdrifts.</p>
<h2>Can Mars keep the oceans alive?</h2>
<p>Our findings extend these insights over much longer timescales. Our deep-sea data spanning 65 million years suggest that warmer oceans have more vigorous eddy-driven circulation. </p>
<p>This process may play an important role in a warmer future. In a warming world the difference in temperature between the equator and poles diminishes. This leads to a <a href="https://insideclimatenews.org/news/09022024/climate-impacts-from-collapse-of-atlantic-meridional-overturning-current-could-be-worse-than-expected/">weakening</a> of the world’s <a href="https://www.worldatlas.com/oceans/what-is-the-ocean-conveyor-belt.html">ocean conveyor belt</a>.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/even-temporary-global-warming-above-2-will-affect-life-in-the-oceans-for-centuries-214251">Even temporary global warming above 2℃ will affect life in the oceans for centuries</a>
</strong>
</em>
</p>
<hr>
<p>In such a scenario, oxygen-rich surface waters would no longer mix well with deeper waters, potentially resulting in a <a href="https://johnmenadue.com/humanity-sinking-into-a-stagnant-ocean/#:%7E:text=%E2%80%93%20as%20the%20difference%20in%20temperature,waters%2C%20which%20then%20become%20stagnant">stagnant ocean</a>. Our results and <a href="https://www.annualreviews.org/doi/abs/10.1146/annurev.fluid.36.050802.122121">analyses of deep ocean mixing</a> suggest that more intense deep-ocean eddies may counteract such ocean stagnation. </p>
<p>How the Earth-Mars astronomical influence will interact with shorter Milankovitch cycles and current human-driven global warming will largely depend on the future trajectory of our greenhouse gas emissions.</p><img src="https://counter.theconversation.com/content/225454/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Adriana Dutkiewicz receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Dietmar Müller and Slah Boulila 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>Deep-sea sediments show how the changing orbits of Earth and Mars are linked to past global warming and the speeding up of deep-ocean eddies.Adriana Dutkiewicz, ARC Future Fellow, University of SydneyDietmar Müller, Professor of Geophysics, University of SydneySlah Boulila, Associate lecturer, Sorbonne UniversitéLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2241132024-03-12T18:55:13Z2024-03-12T18:55:13ZSolar eclipses result from a fantastic celestial coincidence of scale and distance<figure><img src="https://images.theconversation.com/files/580531/original/file-20240307-28-al4bnq.jpg?ixlib=rb-1.1.0&rect=23%2C15%2C5247%2C3690&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Solar eclipses happen because of a few factors, including the Moon's size and distance from the Sun. </span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/EclipseKentucky/8b202fc6981149ebb1c59158d49e348d/photo?Query=eclipse&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=478&digitizationType=Digitized&currentItemNo=7&vs=true&vs=true">AP Photo/Timothy D. Easley</a></span></figcaption></figure><p>On April 8, 2024, millions across the U.S. will have the once-in-a-lifetime chance to view a total solar eclipse. <a href="https://science.nasa.gov/eclipses/future-eclipses/eclipse-2024/where-when/">Cities including</a> Austin, Texas; Buffalo, New York; and Cleveland, Ohio, will have a direct view of this rare cosmic event that lasts for just a few hours.</p>
<p>While <a href="https://theconversation.com/astro-tourism-chasing-eclipses-meteor-showers-and-elusive-dark-skies-from-earth-207969">you can see many astronomical events</a>, such as <a href="https://theconversation.com/comets-101-everything-you-need-to-know-about-the-snow-cones-of-space-213342">comets</a> and meteor showers, from anywhere on Earth, eclipses are different. You need to travel to what’s called the <a href="https://theconversation.com/when-the-sun-goes-dark-5-questions-answered-about-the-solar-eclipse-81308">path of totality</a> to experience the full eclipse. Only certain places get an eclipse’s full show, and that’s because of scale. </p>
<p>The relatively small <a href="https://www.space.com/18135-how-big-is-the-moon.html">size of the Moon</a> and its shadow make eclipses truly once-in-a-lifetime opportunities. On average, total solar eclipses are visible somewhere on Earth once every few years. But from any one location on Earth, <a href="https://eclipse.gsfc.nasa.gov/SEcirc/SEcirc.html">it is roughly 375 years</a> between solar eclipses.</p>
<p><a href="https://science.psu.edu/astro/people/cxp137">I’m an astronomer</a>, but I have never seen a total solar eclipse, so I plan to drive to Erie, Pennsylvania, in the path of totality, for this one. This is one of the <a href="https://eclipse.gsfc.nasa.gov/SEmap/SEmapNA/TSENorAm2051.gif">few chances I have</a> to see a total eclipse without making a much more expensive <a href="https://theconversation.com/astro-tourism-chasing-eclipses-meteor-showers-and-elusive-dark-skies-from-earth-207969">trip to someplace more remote</a>. Many people have asked me why nearby eclipses are so rare, and the answer is related to the size of the Moon and its distance from the Sun.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/fmtGqOxxmEU?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Those in the path of totality will have the opportunity to see a total solar eclipse this April.</span></figcaption>
</figure>
<h2>Size and scale</h2>
<p>You can observe a solar eclipse when the Moon passes in front of the Sun, blocking some or all of the Sun from view. For people on Earth to be able to see an eclipse, the Moon, while orbiting around the Earth, must lie exactly along the observer’s line of sight with the Sun. Only some observers will see an eclipse, though, because not everyone’s view of the Sun will be blocked by the Moon on the day of an eclipse. </p>
<p>The fact that solar eclipses happen at all is a bit of a numerical coincidence. It just so happens <a href="https://science.nasa.gov/sun/facts/#hds-sidebar-nav-3">that the Sun</a> is approximately 400 times <a href="https://science.nasa.gov/moon/facts/#hds-sidebar-nav-3">larger than the Moon</a> and also 400 times more distant from the Earth. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/581049/original/file-20240311-22-9ovtoi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A photo showing the Earth next to the Moon. The Earth is much larger." src="https://images.theconversation.com/files/581049/original/file-20240311-22-9ovtoi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/581049/original/file-20240311-22-9ovtoi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/581049/original/file-20240311-22-9ovtoi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/581049/original/file-20240311-22-9ovtoi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/581049/original/file-20240311-22-9ovtoi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/581049/original/file-20240311-22-9ovtoi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/581049/original/file-20240311-22-9ovtoi.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">Earth’s size compared with the Moon. Distances not to scale.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/the-earth-and-moon-to-scale-royalty-free-image/136247709?phrase=earth+moon+size+comparison&adppopup=true">Laara Cerman/Leigh Righton/Stockbyte via Getty Images</a></span>
</figcaption>
</figure>
<p>So, even though the Moon is much smaller <a href="https://science.nasa.gov/sun/facts/">than the Sun</a>, it is just close enough to Earth to appear the same size as the Sun when seen from Earth. </p>
<p>For example, your pinky finger is much, much smaller than the Sun, but if you hold it up at arm’s length, it appears to your eye to be large enough to block out the Sun. The Moon can do the same thing – it can block out the Sun if it’s lined up perfectly with the Sun from your point of view. </p>
<h2>Path of totality</h2>
<p>When the Earth, Moon and Sun line up perfectly, the Moon <a href="https://science.nasa.gov/solar-system/skywatching/eclipses/solar-eclipses/2024-solar-eclipse/total-solar-eclipse-2024-the-moons-moment-in-the-sun/">casts a shadow onto the Earth</a>. Since the Moon is round, its shadow is round as it lands on Earth. The only people who see the eclipse are those in the area on Earth where the shadow lands at a given moment. </p>
<p>The Moon is continuously orbiting around the Earth, so as time goes on during the eclipse, the Moon’s shadow moves over the face of the Earth. Its shadow ends up looking like a thick line that can cover hundreds of miles in length. Astronomers call that line the <a href="https://science.nasa.gov/solar-system/skywatching/eclipses/new-nasa-map-details-2023-and-2024-solar-eclipses-in-the-us/">path of totality</a>. </p>
<p>From any given location along the path of totality, an observer can see the Sun completely eclipsed for a few minutes. Then, the shadow moves away from that location and the Sun slowly becomes more and more visible. </p>
<h2>A tilted orbit</h2>
<p>Solar eclipses don’t happen every single time the Moon passes in between Earth and the Sun. If that were the case, there would be a solar eclipse every month. </p>
<p>If you could float above the Earth’s North Pole and see the Moon’s orbit from above, you would see the Moon line up with the Sun once every time it orbits around the Earth, which is approximately once per month. From this high point of view, it looks like the Moon’s shadow should land on Earth every orbit. </p>
<p>However, if you could shift your perspective to look at the Moon’s orbit from the orbital plane, you would see that the Moon’s orbit is <a href="https://moon.nasa.gov/moon-in-motion/phases-eclipses-supermoons/overview/">tilted by about 5 degrees</a> compared with Earth’s orbit around the Sun. This tilt means that sometimes the Moon is too high and its shadow passes above the Earth, and sometimes the Moon is too low and its shadow passes below the Earth. An eclipse happens only <a href="https://svs.gsfc.nasa.gov/4324/">when the Moon is positioned just right</a> and its shadow lands on the Earth. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/JplGhSC-eGM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">There isn’t an eclipse every time the Moon passes in front of the Sun because of the Moon’s tilted orbit around Earth.</span></figcaption>
</figure>
<p>As time goes on, the Earth and the Moon continue spinning, and <a href="https://www.youtube.com/watch?v=JplGhSC-eGM">eventually the Moon aligns with Earth’s orbit</a> around the Sun at the same moment the Moon passes between the Sun and the Earth. </p>
<p>While only certain cities are in the path of totality for this April’s eclipse, the entire U.S. is still close enough to this path that observers outside of the path of totality will see a <a href="https://nso.edu/for-public/eclipse-map-2024">partial eclipse</a>. In those locations, the Moon will appear to pass in front of part of the Sun, leaving a crescent shape of the Sun still visible at the moment of maximum eclipse.</p><img src="https://counter.theconversation.com/content/224113/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Christopher Palma does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Many people will see a dazzling eclipse this April, but these events are possible only because of the sizes and precise distances between Earth, the Moon and the Sun.Christopher Palma, Teaching Professor, Department of Astronomy & Astrophysics, Penn StateLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2254842024-03-12T17:51:07Z2024-03-12T17:51:07ZOur survey of the sky is uncovering the secrets of how planets are born<figure><img src="https://images.theconversation.com/files/580926/original/file-20240311-22-5v1m89.jpeg?ixlib=rb-1.1.0&rect=22%2C44%2C2978%2C1165&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Discs giving birth to new planets, seen by the Very Large Telescope.</span> <span class="attribution"><span class="source">ESO/C. Ginski, A. Garufi, P.-G. Valegård et al.</span></span></figcaption></figure><p>When we look out to the stars, it is typically not a yearning for the distant depths of outer space that drives us. When we are looking out there, we are truly looking back at ourselves. We try to understand our place in the unimaginable vastness of the universe. </p>
<p>One of the most burning questions that drives us is how unique we are. Did life only emerge here on Earth or is our galaxy teaming with it? </p>
<p>The very first step in finding out is to understand how special the Earth really is – and, by extension, our entire Solar System. This requires knowledge about how solar systems actually form. And that’s exactly what <a href="https://www.eso.org/public/news/eso2405/">my colleagues and I have started to uncover</a> with a new series of studies of star-forming regions.</p>
<p>In the past decades, astronomers <a href="https://theconversation.com/explainer-how-do-you-find-exoplanets-24153">have spotted</a> more than 5,000 planets around distant stars – so called exoplanets. We now know that planets are so abundant that you can look up to almost any star in the night sky and be near certain that planets are circling around it. But what do these planets look like?</p>
<p>The first planet that was discovered around a star similar to the Sun came as a shock to us. It was a so-called <a href="https://exoplanets.nasa.gov/resources/1040/hot-jupiter/">hot Jupiter</a>, a massive gas giant that orbits its parent star on such a tight orbit that the length of a year is only four days. This is a truly alien world with no equal in our own solar system.</p>
<p>From this first groundbreaking discovery, astronomers have gone on and found tightly packed systems of super-Earths, rocky planets several times as massive as the Earth, as well as awesome gas giants in century-long orbits around their parent star. Of the many planetary systems that we have found, none equals our own solar system. In fact <a href="https://theconversation.com/more-than-1-000-new-exoplanets-discovered-but-still-no-earth-twin-59274">most of them are quite different.</a> </p>
<p>To understand how all of these different systems come to be, we have to turn to the very beginning. And that’s majestic discs of dust and gas that surround the youngest stars. These are the nurseries which will eventually bring forth new planetary systems. </p>
<p>These discs <a href="https://arxiv.org/abs/2002.00405">are enormous objects</a>, up to several hundred times as extended as the distance between the Earth and the Sun. Yet in the sky they appear tiny. This is because even the nearest ones, which are practically in our galactic backyard, are between 600 and 1,600 light years away.</p>
<p>That is a tiny distance when you consider that the Milky Way galaxy has a diameter of more than 100,000 light years, but it still means that light, the fastest thing in the universe, takes up to 1,600 years to reach us from there. </p>
<p>The typical size of one of these planetary nurseries, as seen from the Earth, would be an angle of 1 “arc-second” on sky, which is equivalent to a 3,600th part of a degree. To put it in perspective, it is like trying to observe a person standing on top of the Eiffel Tower from 500km away in the Dutch capital of Amsterdam. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/UGuIIeFipfk?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>To observe these discs we need the most advanced and largest telescopes. And we need sophisticated instruments that can correct for atmospheric turbulence which blurs our images. This is no mean feat of engineering, with the latest generation of instruments only being available since about a decade. </p>
<h2>New findings</h2>
<p>Using the European Southern Observatory’s “<a href="https://www.eso.org/public/unitedkingdom/teles-instr/paranal-observatory/vlt/">Very Large Telescope</a>”, the VLT, and the <a href="https://www.eso.org/sci/facilities/paranal/instruments/sphere.html">Sphere extreme adaptive optics camera</a>, we have now started to survey nearby young stars.</p>
<p>Our team, consisting of scientists from more than ten countries was able to observe more than 80 of these young stars in amazing detail – with our findings published in a <a href="https://www.eso.org/public/news/eso2405/">series of papers</a> in the journal Astronomy and Astrophysics.</p>
<p>All the images were taken in near infrared light, invisible to the human eye. They show the light from the distant young stars as it is reflected from the tiny dust particles in the discs. This dust is much like sand on the beach and will eventually clump together to form new planets. </p>
<p>What we found was an astonishing diversity of shape and form of these planetary nurseries. Some of them have huge ring systems, others large spiral arms. Some of them are smooth and calm, and yet others are caught in the middle of a storm as dust and gas from the surrounding star-forming clouds rains down on them. </p>
<p>While we expected some of this diversity, our survey shows for the first time that this holds true even within the same star-forming regions. So even planetary systems that form within the same neighbourhood might look quite different from one another.</p>
<figure class="align-center ">
<img alt="Planet-forming discs within the gas-rich cloud of Chamaeleon I, roughly 600 light-years from Earth." src="https://images.theconversation.com/files/581242/original/file-20240312-22-tc1s5x.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/581242/original/file-20240312-22-tc1s5x.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=430&fit=crop&dpr=1 600w, https://images.theconversation.com/files/581242/original/file-20240312-22-tc1s5x.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=430&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/581242/original/file-20240312-22-tc1s5x.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=430&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/581242/original/file-20240312-22-tc1s5x.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=540&fit=crop&dpr=1 754w, https://images.theconversation.com/files/581242/original/file-20240312-22-tc1s5x.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=540&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/581242/original/file-20240312-22-tc1s5x.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=540&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Planet-forming discs within the gas-rich cloud of Chamaeleon I, roughly 600 light-years from Earth.</span>
<span class="attribution"><span class="source">Ginski et, al 2024</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Finding such wide range of discs suggests that the huge diversity in exoplanets discovered so far is a consequence of this broad spectrum of planetary nurseries. </p>
<p>Unlike the Sun, most stars in our galaxy have companions, with two or more stars orbiting a shared centre of mass. When looking at the constellation of Orion, we found that stars in groups of two or more were less likely to have large planet-forming discs than lone stars. This is a useful thing to know when hunting for exo-planets. </p>
<p>Another interesting finding was how uneven the discs in this region were, suggesting they may host massive planets that warp the discs. </p>
<p>The next step in our research will be to connect specific planets to their nurseries, to understand how the different systems might have formed in detail. We also want to zoom in even closer in the innermost regions of these discs in which terrestrial planets like our own Earth might already be forming.</p>
<p>For this, we will use the next generation of telescopes spearheaded by the “<a href="https://elt.eso.org/">Extremely Large Telescope</a>” of the European Southern Observatory that is right now under construction in the Chilean Atacama desert. </p>
<p>There are many questions to answer. But thanks to our survey we now know that the very first step on the long way for life to emerge is an utterly beautiful one.</p><img src="https://counter.theconversation.com/content/225484/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Christian Ginski works for the University of Galway and frequently works with ESO facilities. </span></em></p>Astronomers have spotted a surprisingly diverse set of planet-forming disks.Christian Ginski, Lecturer of astronomy, University of GalwayLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2213812024-03-12T17:44:46Z2024-03-12T17:44:46ZTotal solar eclipses, while stunning, can damage your eyes if viewed without the right protection<figure><img src="https://images.theconversation.com/files/580528/original/file-20240307-30-bxdz7t.jpg?ixlib=rb-1.1.0&rect=47%2C6%2C4468%2C2383&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Solar eclipses don't come around often, but make sure to view these rare events with eclipse glasses to protect your vision. </span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/USEclipseSchools/0f2e25e7620440c0be042b6516d1acde/photo?Query=eclipse%20viewing&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=524&digitizationType=Digitized&currentItemNo=18&vs=true&vs=true">AP Photo/Charlie Riedel</a></span></figcaption></figure><p>On April 8, 2024, and for the second time in the past decade, people in the U.S. will have an opportunity to <a href="https://science.nasa.gov/eclipses/future-eclipses/eclipse-2024/">view a total solar eclipse</a>. But to do so safely, you’ll need to <a href="https://preventblindness.org/get-ready-for-the-next-eclipse/">wear proper protection</a>, or risk eye damage.</p>
<p>Earth is the only planet in our solar system where <a href="https://theconversation.com/when-the-sun-goes-dark-5-questions-answered-about-the-solar-eclipse-81308">solar eclipses can occur</a>. During these celestial events, the Moon passes between our planet and the Sun, blocking the Sun and casting a shadow over the Earth. Total eclipses rarely happen multiple times in the same region of a country during one’s lifetime. </p>
<p>The path of totality for <a href="https://science.nasa.gov/eclipses/">this spring’s eclipse</a>, where you can view the total eclipse, will extend over a 100-mile path that crosses through Mexico, Texas, New England and eastern Canada.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/fmtGqOxxmEU?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Those in the path of totality will have the opportunity to see a total solar eclipse this April.</span></figcaption>
</figure>
<p>As excitement for the celestial show grows across the country, <a href="https://www.forbes.com/sites/jamiecartereurope/2024/03/09/11-ways-to-find-your-last-minute-hotel-for-the-total-solar-eclipse---but-be-quick/?sh=415b5585f4e2">hotels in the path of totality</a> have been booked up by eclipse enthusiasts. Museums and schools have <a href="https://solarsystem.nasa.gov/embeddable-eclipse-events/">planned viewing events</a>, and researchers have developed technology for the <a href="https://astrolab.fas.harvard.edu/LightSound.html">visually impaired and those with hearing loss</a> so more people have the opportunity to experience the eclipse.</p>
<p>Seeing an eclipse is a rare and special opportunity, but <a href="https://directory.hsc.wvu.edu/Profile/28506">as an ophthalmologist</a>, I know that looking directly at the Sun, even for a few moments, can severely damage your eyes. With a few easy precautions, eclipse viewers can protect themselves from severe and irreparable eye damage and vision loss.</p>
<h2>Safe eclipse viewing</h2>
<p>This year’s eclipse will unfold over a 75-minute period, from the moment the Moon starts to partially block the Sun until it completely moves away from it again. </p>
<p>During the partial eclipse period, when the Moon is partly blocking the Sun, you should never look directly at the Sun nor through binoculars, <a href="https://www.masterclass.com/articles/how-to-photograph-a-solar-eclipse">cameras</a> or <a href="https://www.space.com/how-to-photograph-a-solar-eclipse-with-a-smartphone">cellphones</a>. Sunglasses, photographic filters, exposed color film and welding glasses will dim the sunlight, but these items do not prevent <a href="https://www.aao.org/eye-health/tips-prevention/solar-eclipse-eye-safety">eye damage from the Sun’s very intense light rays</a>. </p>
<p>Only <a href="https://preventblindness.org/solar-eclipse-glasses/">solar eclipse glasses</a> with filters designed specifically for observing the partial eclipse are safe to use. They are easily available <a href="https://www.cnn.com/cnn-underscored/outdoors/best-solar-eclipse-glasses?cid=ios_app">from a variety of sources</a>, and you can wear them by themselves or over your glasses or contact lenses. </p>
<p>Keep in mind that these safety filters will permit you to view only the eclipse, as they blacken out everything around you but the Sun itself. Before purchasing a pair, make sure your eclipse glasses are approved by the <a href="https://eclipse.aas.org/eye-safety/iso-certification">ISO 12312-2 international standard</a>.</p>
<p>Only during its <a href="https://eclipse.gsfc.nasa.gov/SEhelp/SEglossary.html">period of totality</a>, the time when the Sun is fully behind the Moon, is it safe to remove your filtered glasses – and then only with caution.</p>
<p>This year, totality will last an unusually long <a href="https://science.nasa.gov/eclipses/future-eclipses/eclipse-2024/">four and a half minutes</a>. If you leave your eclipse glasses on, you will miss seeing the Sun’s bright ring, or corona, behind the Moon. But then, as the Moon moves on, the sky will brighten and you’ll need to put the eclipse glasses back on.</p>
<h2>Eyes and light</h2>
<p>While the pupils of our eyes naturally constrict to limit bright light, and our eyes have pigments to absorb light, direct sunlight overwhelms these functions. Even viewing the Sun for a few brief moments <a href="https://theconversation.com/turn-around-bright-eyes-heres-how-to-see-the-eclipse-and-protect-your-vision-203571">can cause permanent vision loss</a>. </p>
<p>The Sun emits intense <a href="https://www.britannica.com/science/sunlight-solar-radiation">ultraviolet and infrared light</a>, which, while not visible to the human eye, can burn sensitive ocular tissues, such as the cornea and retina.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/581353/original/file-20240312-24-e55u1i.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram of an eye as viewed from the side." src="https://images.theconversation.com/files/581353/original/file-20240312-24-e55u1i.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/581353/original/file-20240312-24-e55u1i.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=486&fit=crop&dpr=1 600w, https://images.theconversation.com/files/581353/original/file-20240312-24-e55u1i.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=486&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/581353/original/file-20240312-24-e55u1i.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=486&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/581353/original/file-20240312-24-e55u1i.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=611&fit=crop&dpr=1 754w, https://images.theconversation.com/files/581353/original/file-20240312-24-e55u1i.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=611&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/581353/original/file-20240312-24-e55u1i.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=611&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 cornea is the clear front surface of the eye, which lets light in. The retina is the inner lining of the back part of the eye, which sends signals to your brain, allowing you to see.</span>
<span class="attribution"><a class="source" href="https://aapos.org/glossary/how-to-safely-view-a-solar-eclipse">American Association for Pediatric Ophthalmology and Strabismus</a></span>
</figcaption>
</figure>
<p>Corneal damage from sunlight, called <a href="https://www.mayoclinic.org/diseases-conditions/actinic-keratosis/symptoms-causes/syc-20354969">solar keratosis</a>, can blur vision and be quite painful. While the cornea can heal itself, it may require several days to get better and lead to lost time at work or school. </p>
<p>Retinal damage, called <a href="https://www.health.wa.gov.au/Articles/S_T/Solar-retinopathy">solar retinopathy</a>, occurs inside the eye. While it isn’t painful, it can be more severe than corneal damage and can dramatically impair vision. Solar retinopathy symptoms include a blind spot in one’s central vision, visual distortions and altered color vision. </p>
<p>In mild cases, these symptoms may go away, but in more severe cases, and even with treatment, <a href="https://aapos.org/glossary/how-to-safely-view-a-solar-eclipse">they may become permanent</a>. </p>
<p>To both enjoy the eclipse and prevent eye damage, make sure you and your loved ones all view the event with strict proper precautions.</p><img src="https://counter.theconversation.com/content/221381/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Geoffrey Bradford does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Now’s the time to get your hands on a pair of eclipse glasses in preparation for April’s display of celestial wonder.Geoffrey Bradford, Professor of Pediatrics and Ophthalmology, West Virginia UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2076982024-03-12T12:29:40Z2024-03-12T12:29:40ZNASA’s search for life on Mars: a rocky road for its rovers, a long slog for scientists – and back on Earth, a battle of the budget<p>Is or was there life on Mars? That profound question is so complex that it will not be fully answered by the <a href="https://mars.nasa.gov/">two NASA rovers now exploring it</a>. </p>
<p>But because of the literal groundwork the rovers are performing, scientists are finally investigating, in-depth and in unprecedented detail, the planet’s evidence for life, known as its “<a href="https://astrobiology.nasa.gov/education/alp/what-is-a-biosignature/">biosignatures</a>.” This search is remarkably complicated, and in the case of Mars, it is spanning decades. </p>
<p><a href="https://geology.ufl.edu/people/faculty/dr-amy-j-williams-2/">As a geologist</a>, I have had the extraordinary opportunity to work on both the Curiosity and Perseverance rover missions. Yet as much as scientists are learning from them, it will take another robotic mission to figure out if Mars has ever hosted life. That mission will bring Martian rocks back to Earth for analysis. Then – hopefully – we will have an answer. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/578822/original/file-20240229-16-zmsstx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A photograph of the planet Mars, showing white caps and the reddish Martian surface." src="https://images.theconversation.com/files/578822/original/file-20240229-16-zmsstx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/578822/original/file-20240229-16-zmsstx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=564&fit=crop&dpr=1 600w, https://images.theconversation.com/files/578822/original/file-20240229-16-zmsstx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=564&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/578822/original/file-20240229-16-zmsstx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=564&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/578822/original/file-20240229-16-zmsstx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=708&fit=crop&dpr=1 754w, https://images.theconversation.com/files/578822/original/file-20240229-16-zmsstx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=708&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/578822/original/file-20240229-16-zmsstx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=708&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 photograph of Mars, the fourth planet from the Sun, taken by the Hubble Space Telescope in 2017.</span>
<span class="attribution"><a class="source" href="https://science.nasa.gov/image-detail/amf-gsfc_20171208_archive_e000019/">NASA</a></span>
</figcaption>
</figure>
<h2>From habitable to uninhabitable</h2>
<p>While so much remains mysterious about Mars, there is one thing I am confident about. Amid the thousands of pictures both rovers are taking, I’m quite sure no alien bears or meerkats will show up in any of them. Most scientists doubt the surface of Mars, or its near-surface, could currently sustain even single-celled organisms, much less complex forms of life. </p>
<p>Instead, the rovers are acting as extraterrestrial detectives, hunting for clues that life may have existed eons ago. That includes evidence of long-gone liquid surface water, life-sustaining minerals and organic molecules. To find this evidence, <a href="https://mars.nasa.gov/msl/home/">Curiosity</a> and <a href="https://mars.nasa.gov/mars2020/">Perseverance</a> are treading very different paths on Mars, more than 2,000 miles (3,200 kilometers) from each other. </p>
<p>These two rovers will help scientists answer some big questions: Did life ever exist on Mars? Could it exist today, perhaps deep under the surface? And would it be only microbial life, or is there any possibility it might be more complex? </p>
<p>The Mars of today is nothing like the <a href="https://www.nasa.gov/solar-system/nasa-funded-study-extends-period-when-mars-could-have-supported-life/#:%7E">Mars of several billion years ago</a>. In its infancy, Mars was far more Earth-like, with a thicker atmosphere, rivers, lakes, maybe even oceans of water, and the essential elements needed for life. But this period was cut short when Mars <a href="https://mgs-mager.gsfc.nasa.gov/#:%7E">lost its magnetic field</a> and nearly all of its atmosphere – now only 1% as dense as the Earth’s. </p>
<p>The change from habitable to uninhabitable took time, perhaps hundreds of millions of years; if life ever existed on Mars, it likely died out a few billion years ago. Gradually, Mars became the cold and dry desert that it is today, with a landscape comparable to <a href="https://www.alluringworld.com/mcmurdo-dry-valleys/">the dry valleys of Antarctica</a>, without glaciers and plant or animal life. The average Martian temperature is minus 80 degrees Fahrenheit (minus 62 degrees Celsius), and its meager atmosphere is nearly all carbon dioxide. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/579676/original/file-20240304-28-76rhqs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="The Perseverance rover, dusty and dirty, parked in a patch of Martian soil." src="https://images.theconversation.com/files/579676/original/file-20240304-28-76rhqs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/579676/original/file-20240304-28-76rhqs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=551&fit=crop&dpr=1 600w, https://images.theconversation.com/files/579676/original/file-20240304-28-76rhqs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=551&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/579676/original/file-20240304-28-76rhqs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=551&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/579676/original/file-20240304-28-76rhqs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=692&fit=crop&dpr=1 754w, https://images.theconversation.com/files/579676/original/file-20240304-28-76rhqs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=692&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/579676/original/file-20240304-28-76rhqs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=692&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 Mars rover Perseverance has taken over 200,000 pictures, including this selfie from April, 2021.</span>
<span class="attribution"><a class="source" href="https://mars.nasa.gov/resources/25790/perseverances-selfie-with-ingenuity/">NASA/JPL-Caltech/MSSS</a></span>
</figcaption>
</figure>
<h2>Early exploration</h2>
<p>Robotic exploration of the Martian surface began in the 1970s, when life-detection experiments on the <a href="https://mars.nasa.gov/mars-exploration/missions/viking-1-2/">Viking missions</a> failed to find any conclusive evidence for life. </p>
<p><a href="https://www.jpl.nasa.gov/missions/mars-pathfinder-sojourner-rover">Sojourner, the first rover</a>, landed in 1997 and demonstrated that a moving robot could perform experiments. In 2004, <a href="https://mars.nasa.gov/mer/">Spirit and Opportunity</a> followed; both found evidence that liquid water once existed on the Martian surface. </p>
<p>The Curiosity rover <a href="https://mars.nasa.gov/msl/home/">landed in 2012</a> and began ascending Mount Sharp, the 18,000-foot-high mountain located inside Gale crater. There is a reason why NASA chose it as an exploration site: The mountain’s rock layers show <a href="https://www.jpl.nasa.gov/news/mars-rover-views-spectacular-layered-rock-formations">a dramatic shift in climate</a>, from one with abundant liquid water to the dry environment of today. </p>
<p>So far, Curiosity has found evidence in several locations of past liquid water, minerals that may provide chemical energy, and intriguingly, a <a href="https://doi.org/10.1029/2021JE007107">variety of organic carbon molecules</a>. </p>
<p>While organic carbon is not itself alive, it is a building block <a href="https://www.nasa.gov/solar-system/nasas-curiosity-takes-inventory-of-key-life-ingredient-on-mars/">for all life as we know it</a>. Does its presence mean that life once existed on Mars?</p>
<p>Not necessarily. Organic carbon can be abiotic – that is, unrelated to a living organism. For example, maybe the organic carbon came from a <a href="https://www.livescience.com/tissint-meteorite-organic-compounds">meteorite that crashed on Mars</a>. And though the rovers carry wonderfully sophisticated instruments, they can’t definitively tell us if these organic molecules are related to past life on Mars.</p>
<p>But laboratories here on Earth likely can. By collecting rock and soil samples from the Martian surface, and then returning them to Earth for detailed analysis with our state-of-the-art instruments, scientists may finally have the answer to an age-old question.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/YPNVVDphQVc?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">An animation of the proposed Mars Sample Return mission.</span></figcaption>
</figure>
<h2>Perseverance</h2>
<p>Enter Perseverance, NASA’s <a href="https://mars.nasa.gov/mars2020/">newest flagship mission to Mars</a>. For the past three years – it landed in February 2021 – Perseverance has been searching for signs of bygone microbial life in the rocks within Jezero crater, selected as the landing site because it once contained a large lake. </p>
<p>Perseverance is the first step of the <a href="https://mars.nasa.gov/msr/">Mars Sample Return</a> mission, an international effort to collect Martian rock and soil for return to Earth.</p>
<p>The instrument suite onboard Perseverance will help the science team choose the rocks that seem to promise the most scientific return. This will be a careful process; after all, there would be only <a href="https://mars.nasa.gov/msr/multimedia/videos/?v=523">30 seats on the ride back to Earth</a> for these geological samples.</p>
<h2>Budget woes</h2>
<p>NASA’s original plan called for returning those samples to Earth by 2033. But work on the mission – now estimated to cost between US$8 billion to $11 billion – has slowed <a href="https://www.cbsnews.com/losangeles/news/jpl-to-lay-off-more-than-500-employees/">due to budget cuts and layoffs</a>. The cuts are severe; a request for $949 million to fund the mission for fiscal 2024 <a href="https://www.latimes.com/science/story/2024-03-06/nasa-budget-deal-hope-for-mars-sample-return-mission-jpl">was trimmed to $300 million</a>, although efforts are underway to <a href="https://spacenews.com/congressional-letter-asks-white-house-to-reverse-msr-spending-cuts/">restore at least some of the funding</a>. </p>
<p>The Mars Sample Return mission is critical to better understand the potential for life beyond Earth. The science and the technology that will enable it are both novel and expensive. But if NASA discovers life once existed on Mars – even if it’s by finding a microbe dead for a billion years – that will tell scientists that life is not a fluke one-time event that only happened on Earth, but a more common phenomenon that could occur on many planets.</p>
<p>That knowledge would revolutionize the way human beings see ourselves and our place in the universe. There is far more to this endeavor than just returning some rocks.</p><img src="https://counter.theconversation.com/content/207698/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Amy J. Williams receives funding from NASA Participating Scientist grants associated with the Mars 2020 Perseverance rover and the Mars Science Laboratory Curiosity rover. </span></em></p>Determining whether or not life exists on another planet is an extraordinarily complicated – and expensive – scientific endeavor.Amy J. Williams, Assistant Professor of Geology, University of FloridaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2227092024-03-11T20:26:45Z2024-03-11T20:26:45ZArcheoastronomy uses the rare times and places of previous total solar eclipses to help us measure history<figure><img src="https://images.theconversation.com/files/580911/original/file-20240311-28-ygi764.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C1280%2C1280&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A photograph of the 2017 total solar eclipse, taken at the Oregon State Fair Grounds, Salem, Ore.</span> <span class="attribution"><span class="source">(Dominic Hart/NASA)</span></span></figcaption></figure><p>In 648 BCE, the Greek poet Archilochus wrote that, “nothing can be surprising any more or impossible or miraculous, now that Zeus, father of the Olympians has <a href="https://articles.adsabs.harvard.edu/pdf/2020JAHH...23...47S">made night out of noonday</a>, hiding the light of the gleaming Sun.”</p>
<p>Total solar eclipses have fascinated and terrified people for centuries. Today, we know that total solar eclipses — like the <a href="https://theconversation.com/on-april-8-2024-parts-of-ontario-quebec-the-maritimes-and-newfoundland-will-see-a-total-eclipse-of-the-sun-heres-how-to-get-ready-for-it-203382">upcoming eclipse on April 8</a> — are caused by a cosmic coincidence when the moon comes between the Earth and the sun, momentarily blocking the sun from view. But in ancient times, the cause was unknown.</p>
<p>Nevertheless, the peoples of those eras took note. From all ends of the Earth, stories abound of day turning to night or <a href="https://eclipse2017.nasa.gov/eclipse-history">the sun being consumed</a>, and these records are opening up a new branch of study.</p>
<p><a href="https://www.jstor.org/stable/20170165">Astroarcheology</a> — also called archeoastronomy — uses astronomical records to help date key moments or events in history. Of all astronomical phenomena, total solar eclipses are among the best measuring sticks because they are only visible at a certain time and place. </p>
<p>Total solar eclipses are rare enough that a given spot on Earth is only likely to see <a href="https://articles.adsabs.harvard.edu/pdf/1982JBAA...92..124M">one every 375 years (on average)</a>. And when an eclipse does happen, it only appears as total to those who are <a href="https://eclipsewise.com/solar/SEatlas/SEatlas.html">along a narrow path on Earth</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/580844/original/file-20240310-26-te2a9p.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="(drawing of a solar eclipse represented by a black circle surrounded by a white aura on a black background)" src="https://images.theconversation.com/files/580844/original/file-20240310-26-te2a9p.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/580844/original/file-20240310-26-te2a9p.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=464&fit=crop&dpr=1 600w, https://images.theconversation.com/files/580844/original/file-20240310-26-te2a9p.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=464&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/580844/original/file-20240310-26-te2a9p.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=464&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/580844/original/file-20240310-26-te2a9p.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=583&fit=crop&dpr=1 754w, https://images.theconversation.com/files/580844/original/file-20240310-26-te2a9p.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=583&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/580844/original/file-20240310-26-te2a9p.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"></a>
<figcaption>
<span class="caption">An illustration of the solar eclipse that occurred on Jan. 22, 1898 in India.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Solar_eclipse_of_January_22,_1898">(Edward Walter Maunder/British Astronomical Association)</a></span>
</figcaption>
</figure>
<h2>Identifying years</h2>
<p>This combination of rare time and place helps researchers narrow down the exact date ancient peoples viewed a recorded eclipse. Additional clues such as the time of day the eclipse occurred (morning, noon or evening), time of year (season) or the presence of bright planets can also help identify the exact eclipse.</p>
<p>For example, a record of total solar eclipse occurring near dawn in ancient Chinese texts pertaining to King Yi helped <a href="https://articles.adsabs.harvard.edu/pdf/2003JAHH....6...53L">identify the year his reign began</a>.</p>
<p>One of the oldest recorded eclipses is on a clay tablet from the city of <a href="https://www.britannica.com/place/Ugarit">Ugarit, in modern-day Syria</a>. The city was overthrown after the eclipse, making the tablet one of the last things written down by someone from that city. The inscription on the tablet reads: “… day of the new moon in ḫiyaru the Sun went down, its gate-keeper was [Rashap].”</p>
<p>The word ḫiyaru refers to a time of year around February/March, and Rashap is likely a planet. Armed with this information and knowledge that the city disappeared in the Bronze Age, researchers dated the tablet and eclipse to March 5, 1222 BCE, over 3,000 years ago, with the planet Mars <a href="https://doi.org/10.1038/338238a0">visible near to the eclipsed sun</a>. Thanks to this eclipse, we know that Ugarit fell after March 5, 1222 BCE. </p>
<p>Records like these help researchers identify precise dates in the ancient world.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/580919/original/file-20240311-17800-m97ekg.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="an illustration of text above a photograph of a grey clay tablet" src="https://images.theconversation.com/files/580919/original/file-20240311-17800-m97ekg.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/580919/original/file-20240311-17800-m97ekg.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=689&fit=crop&dpr=1 600w, https://images.theconversation.com/files/580919/original/file-20240311-17800-m97ekg.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=689&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/580919/original/file-20240311-17800-m97ekg.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=689&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/580919/original/file-20240311-17800-m97ekg.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=866&fit=crop&dpr=1 754w, https://images.theconversation.com/files/580919/original/file-20240311-17800-m97ekg.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=866&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/580919/original/file-20240311-17800-m97ekg.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=866&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Photograph and illustration of the clay tablet KTU 1.78 from Ugarit, in modern-day Syria, which mentions a total solar eclipse.</span>
<span class="attribution"><span class="source">(Dietrich and Loretz/University of Chicago Library)</span></span>
</figcaption>
</figure>
<h2>Changing predictions</h2>
<p>Precisely predicting future eclipses, or plotting the paths of historical eclipses, requires knowing the positions of the sun, moon and Earth. Computers can track the motions of each, but the challenge here is that these motions are not constant. As the moon causes tides in Earth’s oceans, the process also causes the moon to slowly drift away from the Earth and <a href="https://www.scientificamerican.com/article/earth-rotation-summer-solstice/">the length of day on Earth to slowly increase</a>. </p>
<p>Essentially, the length of a day on Earth is getting longer by roughly 18 microseconds every year, <a href="http://dx.doi.org/10.1098/rspa.2016.0404">or one second every 55,000 years</a>. After hundreds or thousands of years, that fraction of a second per day adds up to several hours.</p>
<p>The change in Earth’s day also affects dating historical eclipses — if the difference in the length of day is not corrected for, calculations may be inaccurate by thousands of kilometers. As such, when using eclipses to date historical events a correction must be applied; uncertainties in the correction can make <a href="https://doi.org/10.1093/pasj/56.1.215">ancient eclipse identifications</a> harder to pin down in the absence of <a href="https://www.jstor.org/stable/178278">additional information</a> to help <a href="https://articles.adsabs.harvard.edu/pdf/1995QJRAS..36..397Z">narrow down the possibilities</a>. </p>
<h2>Measuring changing day-lengths</h2>
<p>For those solar eclipses that are well established, they open a window into tracking Earth’s length-of-day across the centuries. By timing eclipses over the last 2,000 years, researchers have mapped out the length of Earth’s day over that same span. The value of 18 microseconds per year is an average, but sometimes the Earth slows down a bit more and sometimes a bit less. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/580922/original/file-20240311-139405-bs1pct.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="a graph showing day lengths over time" src="https://images.theconversation.com/files/580922/original/file-20240311-139405-bs1pct.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/580922/original/file-20240311-139405-bs1pct.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=413&fit=crop&dpr=1 600w, https://images.theconversation.com/files/580922/original/file-20240311-139405-bs1pct.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=413&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/580922/original/file-20240311-139405-bs1pct.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=413&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/580922/original/file-20240311-139405-bs1pct.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=518&fit=crop&dpr=1 754w, https://images.theconversation.com/files/580922/original/file-20240311-139405-bs1pct.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=518&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/580922/original/file-20240311-139405-bs1pct.jpg?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"></a>
<figcaption>
<span class="caption">Change in length of day (lod) for Earth in milliseconds (0.001 s) as measured from eclipse records (black line). The red line shows the average change over 2,000 years, while the grey line shows what we would expect from tidal forces between the Earth and moon only. The green dashed line shows a model fit to the data in black.</span>
<span class="attribution"><a class="source" href="http://dx.doi.org/10.1098/rspa.2016.0404">(F.R. Stephenson, L.V. Morrison and C.Y. Hohenkerk)</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Tides alone can’t explain this pattern — there is something more going on between the moon and the Earth, and the cause is still unknown. This mystery, however, can be explored thanks to solar eclipses. </p>
<p>We can measure a change in length of a day on Earth with instruments now, but we wouldn’t be able to capture that change hundreds or thousands of years back in time without a precise measuring stick and records of eclipses over millennia and across the world. Total solar eclipses allow us to peer into not only our own history, but the history of the Earth itself.</p><img src="https://counter.theconversation.com/content/222709/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sarah Sadavoy receives funding from the National Sciences and Engineering Research Council of Canada (NSERC). </span></em></p>Mentions of total solar eclipses in ancient history help researchers pinpoint precise dates of notable events.Sarah Sadavoy, Assistant Professor, Physics, Engineering Physics & Astronomy, Queen's University, OntarioLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2208242024-03-08T14:35:38Z2024-03-08T14:35:38ZApril’s eclipse will mean interruptions in solar power generation, which could strain electrical grids<figure><img src="https://images.theconversation.com/files/573902/original/file-20240206-16-om8k0f.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C3994%2C2658&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Solar panels in Brazil. </span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/7551d26521224cbf94340e255374a7a7?ext=true">AP Photo/Bruna Prado</a></span></figcaption></figure><p>During the most recent total solar eclipse visible in the U.S., on Aug. 21, 2017, the skies darkened as the Moon crossed in front of the Sun. It blocked out all sunlight – except for that from a golden ring visible around the Moon’s shape, called the corona. Not surprisingly, solar power generation across North America plummeted for several hours, from the first moment the Moon began to obscure the Sun to when the Sun’s disk was clear again. </p>
<p>On April 8, 2024, another <a href="https://theconversation.com/when-the-sun-goes-dark-5-questions-answered-about-the-solar-eclipse-81308">total solar eclipse</a> will track across the U.S., causing perhaps an even greater loss of solar power generation. Although this will be the second total solar eclipse visible in the U.S. in under seven years, these events are a rare occurrence. Nevertheless, they present a unique challenge to power grid operators.</p>
<p><a href="https://dornsife.usc.edu/profile/vahe-peroomian/">I am a space scientist</a> with a passion for teaching physics and astronomy. Though I have seen many partial eclipses of the Sun, I have yet to witness a total solar eclipse. My road trip to Bryce Canyon National Park in Utah in October 2023 to see the “ring of fire” <a href="https://theconversation.com/explainer-what-is-a-solar-eclipse-33019">annular solar eclipse</a> was unforgettable, and April 8 will surely find me handing out <a href="https://theconversation.com/turn-around-bright-eyes-heres-how-to-see-the-eclipse-and-protect-your-vision-203571">eclipse glasses</a> once again.</p>
<h2>When the Moon’s shadow blocks the Sun</h2>
<p>During <a href="https://theconversation.com/explainer-what-is-a-solar-eclipse-33019">a solar eclipse</a>, the Moon partially or completely blocks the view of the Sun. Since the Moon is nearly 400 times smaller than the Sun and nearly <a href="https://www.universetoday.com/17109/the-sun-and-the-moon/">400 times closer</a>, the <a href="https://www.forbes.com/sites/startswithabang/2017/02/08/the-strangest-eclipse-fact-of-all-the-moons-shadow-isnt-a-circle/?sh=be76f8c17bd3">Moon’s shadow</a>, visible from Earth, tapers to a width of <a href="https://cmase.uark.edu/_resources/pdf/nasa/NASAConnect/pathoftotality.pdf">70 to 100 miles</a> (112 to 161 kilometers).</p>
<p>Within this region, called the path of totality, observers see a total solar eclipse. Observers close to but outside this path witness a partial eclipse of the Sun, where the Moon covers a fraction of the Sun’s disk. </p>
<p>During the April 8, 2024, total solar eclipse, the <a href="https://science.nasa.gov/eclipses/future-eclipses/eclipse-2024/where-when/">path of totality</a> in the continental U.S. will extend from Texas in the south to Maine in the northeast. Elsewhere in the U.S., Miami will see a partial eclipse in which a maximum of 46% of the Sun’s disk is obscured. In Seattle, far from the path of totality, the Moon will cover only a maximum of <a href="https://www.timeanddate.com/eclipse/map/2024-april-8">20% of the Sun</a>. In southern Texas, where the path of totality first crosses into the U.S., the eclipse will last just under three hours, with totality a mere 4 minutes and 27 seconds. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/sOpYoO_SK7o?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The path of the 2024 solar eclipse.</span></figcaption>
</figure>
<h2>Increasing reliance on solar power</h2>
<p>The worldwide trend toward renewable energy has seen a significant increase in solar, or photovoltaic, power generation in the last decade. Solar power generation capacity is set to <a href="https://www.iea.org/data-and-statistics/data-tools/renewable-energy-progress-tracker">double worldwide</a> between 2022 and 2028, and the U.S. now has the capacity to generate <a href="https://ember-climate.org/data-catalogue/yearly-electricity-data/">three times more solar energy</a> than at the time of the 2017 total solar eclipse.</p>
<p>The most obvious obstacle to solar power generation is cloud cover. On a cloudy day, the energy produced by solar panels drops to <a href="https://www.forbes.com/home-improvement/solar/solar-panels-cloudy-days-night/">10% to 25%</a> of its output on a sunny day. </p>
<p>The North American power transmission grid is divided into <a href="https://www.nerc.com/AboutNERC/keyplayers/Pages/default.aspx">six major regions</a> and <a href="https://alternativeenergy.procon.org/questions/what-is-the-electricity-grid/">more than 150</a> local and regional subgrids. Electrical system operators in each local grid continuously balance the amount of electricity production with the “load,” or the demand for electricity by consumers. </p>
<p>System operators can tap into energy from <a href="https://science.howstuffworks.com/environmental/energy/power.htm">various power generation mechanisms</a> like solar, wind, hydroelectric, natural gas and coal. Local grids can also import and export electricity to and from their grid as needed.</p>
<p>System operators have accurate models for the amount of solar power generated across the U.S. on a daily basis, and these models account for the parts of the continental U.S. that may have cloudy skies. By pairing solar power generation with battery storage, they can access electricity from solar even when the Sun isn’t shining – on cloudy days or at night. </p>
<p>To plan for an eclipse, electrical system operators need to figure out how much the energy production will drop and how much power people will draw from the reserves. On the day of the 2017 total solar eclipse, for example, solar power generation in the U.S. <a href="https://www.nrel.gov/docs/fy18osti/71147.pdf">dropped 25%</a> below average. </p>
<p>Because solar power production falls quickly during the eclipse’s peak, grid operators may need to tap into reserves at a rate that may strain the <a href="https://www.osha.gov/etools/electric-power/illustrated-glossary/transmission-lines">electrical transmission lines</a>. To try to keep things running smoothly, grid operators will rely on local reserves and minimize power transfer <a href="https://www.nrel.gov/docs/fy18osti/71147.pdf">between grids</a> during the event. This should lessen the burden on transmission lines in local grids and prevent temporary blackouts. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/573903/original/file-20240206-28-khlo8k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Electrical towers and power lines shown against a sunset." src="https://images.theconversation.com/files/573903/original/file-20240206-28-khlo8k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/573903/original/file-20240206-28-khlo8k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/573903/original/file-20240206-28-khlo8k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/573903/original/file-20240206-28-khlo8k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/573903/original/file-20240206-28-khlo8k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/573903/original/file-20240206-28-khlo8k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/573903/original/file-20240206-28-khlo8k.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"></a>
<figcaption>
<span class="caption">Solar eclipses can stress the power grid.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/BidenInfrastructure/9a4ee5858ac74db78eb7d96b1961c275/photo?Query=power%20grid&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=226&digitizationType=Digitized&currentItemNo=17&vs=true&vs=true">AP Photo/Matt Rourke</a></span>
</figcaption>
</figure>
<h2>Renewable energy during eclipses</h2>
<p>Solar isn’t the only type of renewable energy generation that goes down during an eclipse. Since it’s not as sunny, temperatures along the path of the eclipse fall by as much as <a href="https://eclipse2017.nasa.gov/temperature-change-during-totality">10 degrees Fahrenheit</a> (5.5 degrees Celsius). Lower temperatures lead to <a href="https://doi.org/10.1093/astrogeo/atx135">slower wind speeds</a> and less wind power generation. </p>
<p>During the August 2017 eclipse, the loss of renewable power generation added up to nearly <a href="https://www.nrel.gov/docs/fy18osti/71147.pdf">6 gigawatts</a>. That’s equivalent to the energy usage of <a href="https://www.energy.gov/eere/articles/how-much-power-1-gigawatt">600 million LED lightbulbs</a> or <a href="https://www.cnet.com/home/energy-and-utilities/gigawatt-the-solar-energy-term-you-should-know-about/">4.5 million homes</a>. </p>
<p>Grid operators compensated by planning ahead and increasing power generation at <a href="https://www.nrel.gov/docs/fy18osti/71147.pdf">natural gas and coal-powered plants</a>, which don’t depend on sunlight. </p>
<p>Over the duration of the eclipse, this increase in nonrenewable energy use led to approximately <a href="https://www.eia.gov/tools/faqs/faq.php?id=74&t=11">10 million pounds</a> of extra carbon dioxide emissions. That’s about the annual carbon dioxide emissions of 1,000 cars.</p>
<p>On April 8, <a href="https://theconversation.com/astro-tourism-chasing-eclipses-meteor-showers-and-elusive-dark-skies-from-earth-207969">eyes across the U.S. will turn upward</a> to catch a glimpse of the eclipsed Sun.</p>
<p>Thanks to the vigilance of electric grid operators, the lights should stay on, and observers won’t have to worry about anything but the stunning show in the sky.</p><img src="https://counter.theconversation.com/content/220824/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Vahe Peroomian has, in the past, received basic research funding from NASA and the National Science Foundation.</span></em></p>When the Moon blocks the Sun during an eclipse, utility suppliers have to pull power from the grid to make up for gaps in solar energy.Vahe Peroomian, Professor of Physics and Astronomy, USC Dornsife College of Letters, Arts and SciencesLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2245252024-02-28T19:15:08Z2024-02-28T19:15:08ZWhat ended the ‘dark ages’ in the early universe? New Webb data just brought us closer to solving the mystery<figure><img src="https://images.theconversation.com/files/578478/original/file-20240228-16-jfjexw.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C3000%2C2281&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://webbtelescope.org/contents/media/images/2023/107/01GQQF4KP3GNVB12G6R0V8KSGM?news=true">NASA / ESA / CSA / Ivo Labbe (Swinburne) / Rachel Bezanson (University of Pittsburgh) / Alyssa Pagan (STScI)</a></span></figcaption></figure><p>About 400,000 years after the Big Bang, the cosmos was a very dark place. The glow of the universe’s explosive birth had cooled, and space was filled with dense gas – mostly hydrogen – with no sources of light.</p>
<p>Slowly, over hundreds of millions of years, the gas was drawn into clumps by gravity, and eventually the clumps grew big enough to ignite. These were the first stars.</p>
<p>At first their light didn’t travel far, as much of it was absorbed by a fog of hydrogen gas. However, as more and more stars formed, they produced enough light to burn away the fog by “reionising” the gas – creating the transparent universe dotted with brilliant points of light we see today.</p>
<p>But exactly which stars produced the light that ended the dark ages and triggered this so-called “epoch of reionisation”? In <a href="https://www.nature.com/articles/s41586-024-07043-6">research published in Nature</a>, we used a gigantic cluster of galaxies as a magnifying glass to gaze at faint relics of this time – and discovered that stars in small, faint dwarf galaxies were likely responsible for this cosmic-scale transformation.</p>
<h2>What ended the dark ages?</h2>
<p>Most astronomers already agreed that galaxies were the main force in reionising the universe, but it wasn’t clear how they did it. We know that stars in galaxies should make a lot of ionising photons, but these photons need to escape the dust and gas inside their own galaxy to ionise hydrogen out in the space between galaxies.</p>
<p>It hasn’t been clear what kind of galaxies would be able to produce and emit enough photons to get the job done. (And indeed, there are those who think more exotic objects like big black holes may have been responsible.)</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/looking-back-toward-cosmic-dawn-astronomers-confirm-the-faintest-galaxy-ever-seen-207602">Looking back toward cosmic dawn − astronomers confirm the faintest galaxy ever seen</a>
</strong>
</em>
</p>
<hr>
<p>There are two camps among adherents of the galaxy theory. </p>
<p>The first thinks huge, massive galaxies produced the ionising photons. There were not many of these galaxies in the early universe, but each one produced a lot of light. So if a certain fraction of that light managed to escape, it might have been enough to reionise the universe.</p>
<p>The second camp thinks we are better off ignoring the giant galaxies and focussing on the huge number of much smaller galaxies in the early universe. Each one of these would have produced far less ionising light, but with the weight of their numbers they could have driven the epoch of reionisation.</p>
<h2>A magnifying glass 4 million lightyears wide</h2>
<p>Trying to look at anything in the early universe is very hard. The massive galaxies are rare, so they are hard to find. Smaller galaxies are more common but they are very faint, which makes it difficult (and expensive) to get high-quality data.</p>
<p>We wanted a look at some of the faintest galaxies around, so we used a huge group of galaxies called Pandora’s Cluster as a magnifying glass. The enormous mass of the cluster distorts space and time, amplifying the light from objects behind it.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/578484/original/file-20240228-24-wuvfsk.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A photo showing magnified galaxies." src="https://images.theconversation.com/files/578484/original/file-20240228-24-wuvfsk.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/578484/original/file-20240228-24-wuvfsk.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=247&fit=crop&dpr=1 600w, https://images.theconversation.com/files/578484/original/file-20240228-24-wuvfsk.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=247&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/578484/original/file-20240228-24-wuvfsk.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=247&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/578484/original/file-20240228-24-wuvfsk.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=310&fit=crop&dpr=1 754w, https://images.theconversation.com/files/578484/original/file-20240228-24-wuvfsk.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=310&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/578484/original/file-20240228-24-wuvfsk.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=310&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Two of the most distant galaxies ever seen, as magnified by Pandora’s Cluster.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Abell_2744#/media/File:Webb_Finds_Distant_Galaxies_Seen_Behind_Pandora’s_Cluster_(weic2220a).jpeg">NASA / ESA/ CSA / T. Treu (UCLA)</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>As part of the <a href="https://jwst-uncover.github.io">UNCOVER program</a>, we used the James Webb Space Telescope to look at magnified infrared images of faint galaxies behind Pandora’s Cluster.</p>
<p>We first looked at many different galaxies, then chose a few particularly distant (and therefore ancient) ones to examine more closely. (This kind of close examination is expensive, so we could only look at eight galaxies in greater detail.)</p>
<h2>The bright glow of hydrogen</h2>
<p>We selected some sources which were around 0.5% of the brightness of our Milky Way galaxy at that time, and checked them for the telltale glow of ionised hydrogen. These galaxies are so faint they were only visible at all thanks to the magnifying effect of Pandora’s Cluster.</p>
<p>Our observations confirmed that these small galaxies did exist in the very early universe. What’s more, we confirmed they produced around four times as much ionising light as we would consider “normal”. This is at the highest end of what we had predicted, based on our understanding of how early stars formed.</p>
<p>Because these galaxies produced so much ionising light, only a small fraction of it would have needed to escape to reionise the universe. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/unlocking-the-mystery-of-the-first-billion-years-of-the-universe-37368">Unlocking the mystery of the first billion years of the universe</a>
</strong>
</em>
</p>
<hr>
<p>Previously, we had thought that around 20% of all ionising photons would need to escape from these smaller galaxies if they are to be the dominant contributor to reionisation. Our new data suggests even 5% would be sufficient – which is about the fraction of ionising photons we see escaping from modern galaxies.</p>
<p>So now we can confidently say these smaller galaxies could have played a very large role in the epoch of reionisation. However, our study was only based on eight galaxies, all close to a single line of sight. To confirm our results we will need to look at different parts of the sky. </p>
<p>We have new observations planned which will target other large galaxy clusters elsewhere in the universe, to find yet more magnified, faint galaxies to test. If all goes well, we will have some answers in a few years.</p><img src="https://counter.theconversation.com/content/224525/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Themiya Nanayakkara receives funding from Australian Research Council Laureate Fellowship FL180100060. </span></em></p>With the help of a magnifying glass 4 million lightyears wide, astronomers may have solved the riddle of what burned away the hydrogen fog that pervaded the early universe.Themiya Nanayakkara, Senior Scientist at the James Webb Australian Data Centre, Swinburne University of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2245642024-02-27T16:00:16Z2024-02-27T16:00:16ZA black hole discovery could force us to rethink how galaxies came to be<figure><img src="https://images.theconversation.com/files/578316/original/file-20240227-30-ntlqbc.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C3834%2C2155&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://webbtelescope.org/contents/media/images/2021/026/01F8QS893NVRJ6EYF0S46237KP?page=1&Tag=Active%20Galaxies/Quasars">NASA, ESA, Joseph Olmsted (STScI)</a></span></figcaption></figure><p>Peering deep into the infancy of the universe, the European Southern Observatory’s Very Large Telescope (VLT) recently confirmed the discovery of <a href="https://www.nature.com/articles/s41550-024-02195-x">the brightest and fastest growing quasar</a>. Quasars are <a href="https://esahubble.org/wordbank/quasar/">luminous objects in the night sky</a> powered by gas falling into a large black hole at the centre of a galaxy. </p>
<p>The discovery of this record-breaking object was fascinating enough. But another crucial aspect to the announcement is that it raises big questions about galaxy formation in the early universe. In particular, it remains puzzling how this quasar, which existed less than two billion years after the Big Bang, could have grown so large so quickly. Probing this conundrum could even lead to a rethink of how galaxies came to be.</p>
<p>Black holes, the densest objects in the universe, are given this name because their gravitational pull is so incredibly strong that not even light can escape their grasp. How then, can a black hole be the origin of such an intense light source? </p>
<p>Well, in some galaxies, <a href="https://science.nasa.gov/universe/black-holes/">where the black hole is sufficiently large</a>, matter is being drawn in at a ferociously high rate. As it spirals in, violent collisions between gases, dust, and stars result in the emission of huge amounts of light energy. The bigger the black hole, the more violent the collisions and the more light is emitted.</p>
<p>The quasar that was the subject of the latest study, known as J0529-4351, has a mass equivalent to 17 billion suns and is incredibly large. There is a spiralling disk of matter spanning a width of seven light years at the centre of the galaxy and the black hole is growing by accreting (accumulating) this matter. The disk’s width is comparable to the distance between Earth and <a href="https://www.britannica.com/place/Alpha-Centauri">the next nearest star system, Alpha Centauri</a>. </p>
<h2>Hiding in plain sight</h2>
<p>The black hole is growing rapidly by consuming a record-breaking amount of mass, equivalent to one sun each day. This intense accretion of matter releases an amount of radiative energy that’s equivalent to a quadrillion (thousand trillion) suns. </p>
<p>This raises the question of why an object so bright has only just been identified in the night sky, despite decades of astronomical observations. It turns out that this sneaky quasar had been hiding in plain sight.</p>
<p>Despite its astonishing luminosity, J0529-4351 is very distant, meaning that it seamlessly blends in among a sea of dimmer stars that lie much closer to Earth. In fact, this quasar is so far away that the light it emits takes a whopping 12 billion years to reach us here on Earth. </p>
<p>The age of the universe is around 13.7 billion years. So this quasar existed just 1.7 billion years after the <a href="https://science.nasa.gov/universe/the-big-bang/">Big Bang, at the beginning of the Universe</a>. </p>
<p>The universe’s expansion following the Big Bang is what permits us to measure the distance to, and therefore the age of, this quasar. A long-known simple <a href="https://www.bbc.co.uk/bitesize/guides/zphppv4/revision/3">formula called Hubble’s law</a>, states that knowing the velocity that an object is moving away from us allows us to calculate how far away it is.</p>
<figure class="align-center ">
<img alt="Very Large Telescope" src="https://images.theconversation.com/files/578312/original/file-20240227-26-rw2ozs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/578312/original/file-20240227-26-rw2ozs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/578312/original/file-20240227-26-rw2ozs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/578312/original/file-20240227-26-rw2ozs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/578312/original/file-20240227-26-rw2ozs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/578312/original/file-20240227-26-rw2ozs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/578312/original/file-20240227-26-rw2ozs.jpg?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">The object was confirmed using the Very Large Telescope facility in Chile.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/cerro-paranal-atacama-desert-chile-jan-750390019">Framalicious / Shutterstock</a></span>
</figcaption>
</figure>
<p>The collisions that occur as matter spirals into this quasar’s black hole raise it to scorching temperatures of 10,000°C. Under these conditions, the atoms in the system emit a characteristic spectrum of light. </p>
<p>These discrete frequencies of light form a sort of barcode that astronomers can use to identify the elemental compositions of objects in the night sky. As an object that’s emitting light moves away from us, the frequency of that observed light undergoes a shift, much like how the sound frequency of an ambulance siren shifts depending on whether it is driving towards or away from you. </p>
<p>This shift seen in astronomical objects is <a href="http://csep10.phys.utk.edu/OJTA2dev/ojta/c2c/galaxies/expanding/lookback_tl.html">known as redshift</a>. This, along with Hubble’s Law, has permitted both the age and the distance (both these properties are linked in cosmology) of J0529-4351 to be confirmed.</p>
<p>This bright beacon from the early universe has raised an important question that is baffling astronomers: how could this black hole, in such a relatively short period of time, grow so fast into such a massive object? Under well accepted models of the early universe, it should have taken longer for it to grow to this size. </p>
<p>What’s more, by tuning the artificial intelligence (AI) models used to scan telescope data for these unusual objects, more could still be found in the coming years. If they resemble J0529-4351, physicists would need to seriously rethink their models of the early universe and galaxy formation.</p>
<p>The fastest-growing black hole ever observed will be the perfect target for a system <a href="https://www.mpe.mpg.de/ir/gravityplus">called Gravity+</a>, an upcoming upgrade to an instrument on the Very Large Telescope called an interferometer. This interferometer is an ingenious way of combining data from the four separate telescopes that actually make up the VLT. </p>
<p>Gravity+ is designed to accurately measure the rotational speed and mass of black holes directly, especially those that lie far away from the Earth. </p>
<p>Furthermore, <a href="https://elt.eso.org/">the European Southern Observatory’s’s Extremely Large Telescope</a>, a 39-metre diameter reflecting telescope, is currently under construction in the Chilean Atacama Desert. This is designed for detecting the optical and near-infrared wavelengths characteristic of distant quasars and will make identifying and characterising such elusive objects even more likely in the future.</p><img src="https://counter.theconversation.com/content/224564/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Robin Smith 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>The discovery raises big questions about widely accepted models of galaxy formation.Robin Smith, Senior Lecturer in Physics, Sheffield Hallam UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2240412024-02-21T17:27:54Z2024-02-21T17:27:54ZThe brightest object ever observed in the night sky is a black hole that’s growing by the equivalent of one Sun a day<figure><img src="https://images.theconversation.com/files/576981/original/file-20240221-28-83koz3.jpg?ixlib=rb-1.1.0&rect=5%2C5%2C3828%2C2149&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/black-hole-slowly-rotating-space-event-2012670551">Merlin74 / Shutterstock</a></span></figcaption></figure><p><a href="https://www.nature.com/articles/s41550-024-02195-x">A new study</a> published in Nature Astronomy describes the most luminous object ever observed by astronomers. It is a black hole with a mass of 17 billion Suns, swallowing a greater amount of mass than the Sun every single day.</p>
<p>It has been known about for several decades, but since it is so bright, astronomers assumed it must be a nearby star. Only recent observations revealed its extreme distance and luminosity.</p>
<p>The object has been dubbed J0529-4351. This name simply refers to its coordinates on the celestial sphere – a way of projecting the objects in the sky onto the inside of a sphere. It is a type of <a href="https://esahubble.org/wordbank/quasar/">object called a quasar</a>.</p>
<p>The physical nature of quasars was initially unknown. But in 1963, the visible light from a <a href="https://www.wired.com/2008/08/dayintech-0805/">quasar called 3C 273</a> was split into all its wavelengths (known as its spectrum). This showed that it was located nearly 2 billion light years away. </p>
<p>Given how bright 3C 273 appears to us, and how far away it is, it must be extremely luminous – a term in astronomy that refers to the amount of light emitted by an object in a unit of time. The only known power source for such extreme luminosity was through material falling into a <a href="https://science.nasa.gov/universe/black-holes/">supermassive black hole</a>. Quasars are therefore the most actively growing black holes in the universe.</p>
<h2>Power source</h2>
<p>Supermassive black holes often sit at the centres of galaxies. As with all quasars, J0529-4351 is powered by material, mostly super-heated hydrogen and helium gas, falling into its black hole from the surrounding galaxy. </p>
<p>Roughly one times the Sun’s mass is falling into this black hole every day. Exactly how so much gas can be channelled into the centre of galaxies to increase the mass of black holes is an unanswered question in astrophysics.</p>
<p>At the galaxy’s centre, the gas forms into a thin disk shape. The properties of viscosity (resistance to the flow of matter in space) and friction in the thin disk help heat the gas to tens of thousands of degrees Celsius. This is hot enough to glow when viewed at ultraviolet and visible light wavelengths. It is that glow that we can observe from Earth. </p>
<p>At around 17 billion Suns in mass, J0529-4351 is not the most massive known black hole. One object, at the centre of the galaxy cluster Abell 1201, is <a href="https://www.space.com/largest-known-black-hole-discovered-through-gravitational-lensing">equivalent to 30 billion Suns</a>. However, we need to bear in mind that because of the time taken for light to travel across the vast distance between this object and Earth, we are witnessing it when the universe was only 1.5 billion years old. Its is now around 13.7 billion years old. </p>
<p>So this black hole must have been growing, or accreting, at this rate for a significant fraction of the age of the universe by the time it was observed. The authors believe the gas accretion by the black hole is happening close to the limit placed by the laws of physics. Faster accretion causes a more luminous disk of gas around the black hole which in turn can halt any more material falling in.</p>
<h2>Story of the discovery</h2>
<p>J0529-4351 has been known about for decades, but despite having an accretion disk of gas 15,000 times larger than our Solar System and occupying its own galaxy – which is probably close to the size of the Milky Way – it is so far away, it appears as a single point of light in our telescopes.</p>
<p>This means it is difficult to distinguish from the billions of stars in our own galaxy. To discover that it is in fact a distant, powerful, supermassive black hole required some more complex techniques. Firstly, astronomers collected light from the middle of the infrared waveband (light with much longer wavelengths than those we can see). </p>
<p>Stars and quasars look quite different to one another at those wavelengths. To confirm the observation, a spectrum was taken (much as it was with the quasar 3C 273), using the <a href="https://rsaa.anu.edu.au/observatories/telescopes/anu-23m-telescope">Australian National University’s 2.3 metre telescope</a> at Siding Spring Observatory, New South Wales. </p>
<p>And, as with 3C 273, the spectrum revealed both the nature of the object and how far away it was – 12 billion light years. This highlighted how extreme its luminosity must be.</p>
<h2>Detailed checks</h2>
<p>Despite these measurements, a number of checks needed to be made to confirm the true luminosity of the quasar. Firstly, astronomers needed to make sure that the light had not been magnified by a source in the sky that was closer to Earth. Much like lenses used in spectacles or binoculars, galaxies can act as lenses. They are so dense that they can bend and magnify the light of more distant sources that are perfectly aligned behind them. </p>
<p>Data from the European Space Agency’s Gaia satellite, which has extremely precise measurements of J0529-4351’s position, was used to determine that J0529-4351 is truly a single non-lensed source of light in the sky. This is backed up by more detailed spectra taken with the <a href="https://www.eso.org/public/unitedkingdom/teles-instr/paranal-observatory/vlt/">European Southern Observatory’s Very Large Telescope</a> (VLT) facility in Chile. </p>
<p>J0529-4351 is likely to become a very significant tool for the future study of quasars and black hole growth. The mass of black holes is a fundamental property but is very difficult to measure directly, as there is no standard set of weighing scales for such absurdly large, mysterious objects. </p>
<p>One technique is to measure the effect the black hole has on more diffuse gas orbiting it in large clouds, called the “broad line region”. This gas is revealed in the spectrum through wide “emission lines”, which are caused by electrons jumping between specific energy levels in the ionised gas. </p>
<p>The width of these lines is directly related to the mass of the black hole, but the calibration of this relationship is very poorly tested for the most luminous objects such as J0529-4351. However, because it is so physically large and so luminous, J0529-4351 will be observable by a new instrument being installed on the VLT, <a href="https://www.eso.org/public/unitedkingdom/teles-instr/paranal-observatory/vlt/vlt-instr/gravity+/">called Gravity+</a>. </p>
<p>This instrument will give a direct measurement of the black hole mass and calibrate the relationships used to estimate masses in other high-luminosity objects.</p><img src="https://counter.theconversation.com/content/224041/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Philip Wiseman works at the University of Southampton and is funded by the Science and Technology Facilities Council.</span></em></p>The extreme object could tell us more about the environment around black holes.Philip Wiseman, Research Fellow, Astronomy, University of SouthamptonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2226122024-02-19T19:04:43Z2024-02-19T19:04:43ZThe brightest object in the universe is a black hole that eats a star a day<figure><img src="https://images.theconversation.com/files/573001/original/file-20240202-23-movrvv.jpg?ixlib=rb-1.1.0&rect=0%2C862%2C2000%2C1967&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Cristy Roberts/ANU</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span></figcaption></figure><p>Scientists have no reported evidence of the true conditions in Hell, perhaps because no one has ever returned to tell the tale. Hell has been imagined as a supremely uncomfortable place, hot and hostile to bodily forms of human life. </p>
<p>Thanks to a huge astronomical survey of the entire sky, we have now found what may be the most hellish place in the universe.</p>
<p>In <a href="https://www.nature.com/articles/s41550-024-02195-x">a new paper in Nature Astronomy</a>, we describe a black hole surrounded by the largest and brightest disc of captive matter ever discovered. The object, called J0529-4351, is therefore also the brightest object found so far in the universe.</p>
<h2>Supermassive black holes</h2>
<p>Astronomers have already found around one million fast-growing supermassive black holes across the universe, the kind that sit at the centres of galaxies and are as massive as millions or billions of Suns. </p>
<p>To grow rapidly, they pull stars and gas clouds out of stable orbits and drag them into a ring of orbiting material called an accretion disc. Once there, very little material escapes; the disc is a mere holding pattern for material that will soon be devoured by the black hole.</p>
<p>The disc is heated by friction as the material in it rubs together. Pack in enough material and the glow of the heat gets so bright that it outshines thousands of galaxies and makes the black hole’s feeding frenzy visible to us on Earth, more than 12 billion light years away.</p>
<h2>The fastest-growing black hole in the universe</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/576335/original/file-20240218-22-6pj8yt.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A somewhat noisy photo of a bright white disk and small reddish dot against a dark background." src="https://images.theconversation.com/files/576335/original/file-20240218-22-6pj8yt.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/576335/original/file-20240218-22-6pj8yt.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=599&fit=crop&dpr=1 600w, https://images.theconversation.com/files/576335/original/file-20240218-22-6pj8yt.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=599&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/576335/original/file-20240218-22-6pj8yt.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=599&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/576335/original/file-20240218-22-6pj8yt.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=753&fit=crop&dpr=1 754w, https://images.theconversation.com/files/576335/original/file-20240218-22-6pj8yt.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=753&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/576335/original/file-20240218-22-6pj8yt.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=753&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 brightest thing in the universe: J0529-4351 is a glowing disc of matter around a supermassive black hole, and it is 500 trillion times brighter than the Sun. (The red dot is a neighbouring star.)</span>
<span class="attribution"><a class="source" href="https://www.nature.com/articles/s41550-024-02195-x">Dark Energy Camera Legacy Survey DR10 / Nature Astronomy</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>The accretion disc of J0529-4351 emits light that is 500 trillion times more intense than that of our Sun. Such a staggering amount of energy can only be released if the black hole eats about a Sun worth of material every day. </p>
<p>It must also have a large mass already. Our data indicate J0529-4351 is 15 to 20 billion times the mass of our Sun.</p>
<p>There is no need to be afraid of such black holes. The light from this monster has taken more than 12 billion years to reach us, which means it would have stopped growing long ago.</p>
<p>In the nearby universe, we see that supermassive black holes these days are mostly sleeping giants. </p>
<h2>Black holes losing their grip</h2>
<p>The age of the black hole feeding frenzy is over because the gas floating around in galaxies has mostly been turned into stars. And after billions of years the stars have sorted themselves into orderly patterns: they are mostly on long, neat orbits around the black holes that sleep in the cores of their galaxies. </p>
<p>Even if a star dove suddenly down towards the black hole, it would most likely carry out a slingshot manoeuvre and escape again in a different direction. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-do-black-holes-twinkle-we-studied-5-000-star-eating-behemoths-to-find-out-198996">Why do black holes twinkle? We studied 5,000 star-eating behemoths to find out</a>
</strong>
</em>
</p>
<hr>
<p>Space probes use slingshot manoeuvres like this to get a boost from Jupiter to access hard-to-reach parts of the Solar System. But imagine if space were more crowded, and our probe ran into one coming the other way: the two would crash together and explode into a cloud of debris that would rapidly fall into Jupiter’s atmosphere. </p>
<p>Such collisions between stars were commonplace in the disorder of the young universe, and black holes were the early beneficiaries of the chaos.</p>
<h2>Accretion discs – a no-go zone for space travellers</h2>
<p>Accretion discs are gateways to a place whence nothing returns, but they are also profoundly unfriendly to life in themselves. They are like giant storm cells, whose clouds glow at temperatures reaching several tens of thousands of degrees Celsius. </p>
<p>The clouds are moving faster and faster as we get closer to the hole, and speeds can reach 100,000 kilometres per second. They move as far in a second as the Earth moves in an hour.</p>
<p>The disc around J0529-4351 is seven light years across. That is one and a half times the distance from the Sun to its nearest neighbour, Alpha Centauri.</p>
<h2>Why only now?</h2>
<p>If this is the brightest thing in the universe, why has it only been spotted now? In short, it’s because the universe is full of glowing black holes.</p>
<p>The world’s telescopes produce so much data that astronomers use sophisticated machine learning tools to sift through it all. Machine learning, by its nature, tends to find things that are similar to what has been found before.</p>
<p>This makes machine learning excellent at finding run-of-the-mill accretion discs around black holes – roughly a million have been detected so far – but not so good at spotting rare outliers like J0529-4351. In 2015, a Chinese team almost missed a <a href="https://www.nature.com/articles/nature14241">remarkably fast-growing black hole</a> picked out by an algorithm because it seemed too extreme to be real.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/astronomers-see-ancient-galaxies-flickering-in-slow-motion-due-to-expanding-space-208621">Astronomers see ancient galaxies flickering in slow motion due to expanding space</a>
</strong>
</em>
</p>
<hr>
<p>In our recent work, we were aiming to find all the most extreme objects, the most luminous and most rapidly growing black holes, so we avoided using machine learning tools that were guided by too much prior knowledge. Instead we used more old-fashioned methods to search through new data covering the entire sky, with excellent results.</p>
<p>Our work also depended on Australia’s current 10-year partnership with the European Southern Observatory, an organisation funded by several European countries with a huge array of astronomical facilities.</p><img src="https://counter.theconversation.com/content/222612/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Christian Wolf has received funding from the Australian Research Council. </span></em></p>The black hole J0529-4351 is 500 trillion times brighter than the Sun.Christian Wolf, Associate Professor, Astronomy & Astrophysics, Australian National UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2183302024-02-19T13:36:56Z2024-02-19T13:36:56ZWhy does a leap year have 366 days?<figure><img src="https://images.theconversation.com/files/575717/original/file-20240214-24-h6q6if.jpg?ixlib=rb-1.1.0&rect=38%2C23%2C5137%2C3422&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Leap Day is coming.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/calendar-on-february-29-on-a-leap-year-leap-day-royalty-free-image/1196849410">Marvin Samuel Tolentino Pineda/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>Why does a leap year have 366 days? Does the Earth move slower every four years? – Aarush, age 8, Milpitas, California</p>
</blockquote>
<hr>
<p>You may be used to hearing that it takes the Earth 365 days to make a full lap, but that journey actually lasts about 365 and a quarter days. Leap years help to keep the 12-month calendar matched up with Earth’s movement around the Sun. </p>
<p>After four years, those leftover hours add up to a whole day. In a leap year, we add this extra day to the month of February, making it 29 days long instead of the usual 28.</p>
<p>The idea of an annual catch-up dates back to ancient Rome, where people had a calendar with 355 days instead of 365 because it was based on cycles and phases of the Moon. They noticed that their calendar was getting out of sync with the seasons, so they began adding an extra month, <a href="https://www.britannica.com/science/Roman-republican-calendar">which they called Mercedonius</a>, every two years to catch up with the missing days.</p>
<p>In the year 45 B.C.E., Roman emperor Julius Caesar introduced a solar calendar, based on one developed in Egypt. Every four years, February received an extra day to keep the calendar in line with the Earth’s journey around the Sun. In honor of Caesar, this system is still known as the Julian calendar.</p>
<p>But that wasn’t the last tweak. As time went on, people realized that the Earth’s journey wasn’t exactly 365.25 days – it <a href="https://airandspace.si.edu/stories/editorial/science-leap-year">actually took 365.24219 days</a>, which is about 11 minutes less. So adding a whole day every four years was actually a little more correction than was needed. </p>
<p>In 1582, Pope Gregory XIII signed an order that made a small adjustment. There would still be a leap year every four years, except in “century” years – years divisible by 100, like 1700 or 2100 – unless they were also divisible by 400. It might sound a bit like a puzzle, but this adjustment made the calendar <a href="https://airandspace.si.edu/stories/editorial/science-leap-year">even more accurate</a> – and from that point on, it was known as the Gregorian calendar.</p>
<h2>What if we didn’t have leap years?</h2>
<p>If the calendar didn’t make that small correction every four years, it would gradually fall out of alignment with the seasons. Over centuries, this could lead to the <a href="https://www.britannica.com/story/whats-the-difference-between-a-solstice-and-an-equinox">solstices and equinoxes</a> occurring at different times than expected. Winter weather might develop in what the calendar showed as summer, and farmers could become confused about when to plant their seeds.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/YTOr8_ILqGw?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Without leap years, our calendar would gradually become disconnected from the seasons.</span></figcaption>
</figure>
<p>Other calendars around the world have their own ways of keeping time. The Jewish calendar, which is regulated by <a href="https://www.britannica.com/topic/Jewish-religious-year">both the Moon and the Sun</a>, is like a big puzzle with a 19-year cycle. Every now and then, it adds a leap month to make sure that special celebrations happen at just the right time. </p>
<p>The <a href="https://ing.org/resources/for-all-groups/calendar-of-important-islamic-dates/">Islamic calendar</a> is even more unusual. It follows the <a href="https://spaceplace.nasa.gov/moon-phases/en/">phases of the Moon</a> and doesn’t add extra days. Since a lunar year is only about 355 days long, key dates on the Islamic calendar move 10 to 11 days earlier each year on the solar calendar. </p>
<p>For example, Ramadan, the <a href="https://ing.org/resources/for-all-groups/calendar-of-important-islamic-dates/">Islamic month of fasting</a>, falls in the ninth month of the Islamic calendar. In 2024, it will run from March 11 to April 9; in 2025, it will occur from March 1-29; and in 2026, it will be celebrated from Feb. 18 to March 19.</p>
<h2>Learning from the planets</h2>
<p>Astronomy originated as a way to make sense of our daily lives, linking the events around us to celestial phenomena. The concept of leap years exemplifies how, from early ages, humans found order in conditions that seemed chaotic. </p>
<p>Simple, unsophisticated but effective tools, born from creative ideas of ancient astronomers and visionaries, provided the first glimpses into understanding the nature that envelops us. Some <a href="https://www.britannica.com/science/astronomy/History-of-astronomy">ancient methods</a>, such as <a href="https://sci.esa.int/web/gaia/-/53196-the-oldest-sky-maps">astrometry and lists of astronomical objects</a>, persist even today, revealing the timeless essence of our quest to understand nature. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/575719/original/file-20240214-30-of8z7y.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Photograph of an intricate schematic guide to the night sky." src="https://images.theconversation.com/files/575719/original/file-20240214-30-of8z7y.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/575719/original/file-20240214-30-of8z7y.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=356&fit=crop&dpr=1 600w, https://images.theconversation.com/files/575719/original/file-20240214-30-of8z7y.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=356&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/575719/original/file-20240214-30-of8z7y.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=356&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/575719/original/file-20240214-30-of8z7y.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=447&fit=crop&dpr=1 754w, https://images.theconversation.com/files/575719/original/file-20240214-30-of8z7y.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=447&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/575719/original/file-20240214-30-of8z7y.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=447&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Ancient Egyptians were dedicated astronomers. This section from the ceiling of the tomb of Senenmut, a high court official in Egypt, was drawn sometime circa 1479–1458 B.C.E. It shows constellations, protective gods and 24 segmented wheels for the hours of the day and the months of the year.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Senenmut-Grab.JPG">NebMaatRa/Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>People who do research in physics and astronomy, the <a href="https://scholar.google.com/citations?user=t4L_D18AAAAJ&hl=en">field that I study</a>, are inherently curious about the workings of the universe and our origins. This work is exciting, and also extremely humbling; it constantly shows that in the grand scheme, our lives occupy a mere second in the vast expanse of space and time – even in leap years when we add that extra day.</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/218330/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Bhagya Subrayan does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Humans have synced their calendars to the sun and moon for centuries, but every so often, these systems need a little correction.Bhagya Subrayan, PhD Student in Physics and Astronomy, Purdue UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2232472024-02-12T19:33:22Z2024-02-12T19:33:22ZNewborn gas planets may be surprisingly flat – new research<p>A new planet starts its life in a rotating circle of gas and dust, a cradle known as a <a href="https://esahubble.org/wordbank/circumstellar-disc/">protostellar disc</a>. My colleagues and I have used computer simulations to show that newborn gas planets in these discs are likely to have surprisingly flattened shapes. This finding, <a href="https://www.aanda.org/articles/aa/full_html/2024/02/aa48753-23/aa48753-23.html">published in Astronomy and Astrophysics Letters</a>, could add to our picture of exactly how planets form.</p>
<p>Observing protoplanets that have just formed and are still within their protostellar discs is extremely difficult. Until now only three such young protoplanets have been observed, with two of them in the same system, PDS 70.</p>
<p>We need to find systems that are young, and close enough for our telescopes to be able to detect the dim light from the planet itself and distinguish it from that of the disc. The whole process of planetary formation lasts only a few million years which is nothing more than a blink of an eye in astrophysical scales. This means we need to have luck to catch them in the act of forming.</p>
<p>Our research group performed computer simulations to determine the properties of gaseous protoplanets under a variety of thermal conditions in the planets’ cradles. </p>
<p>The simulations have enough resolution to be able to follow the evolution of a protoplanet in the disc from an early stage, when it is just a mere condensation within the disc. Such simulations are computationally demanding and were run on <a href="https://dirac.ac.uk/">DiRAC, the UK’s astrophysics supercomputing facility</a>.</p>
<p>Typically, multiple planets form within a disc. The study found that protoplanets have a shape known as oblate spheroids, like Smarties or M&M’s, rather than being spherical. They grow by drawing gas predominantly through their poles rather than their equators. </p>
<p>Technically, the planets in our Solar System are also oblate spheroids but their flattening is small. <a href="https://spaceplace.nasa.gov/planets-round/en/#:%7E:text=Mercury%20and%20Venus%20are%20the,bit%20thicker%20in%20the%20middle.">Saturn has a flattening of 10%, Jupiter 6%, whereas Earth a mere 0.3%</a>.</p>
<p>In comparison, the typical flattening of protoplanets is 90%. Such a flattening will affect the observed properties of protoplanets, and it needs to be taken into account when interpreting observations.</p>
<h2>How planets start off</h2>
<p>The most widely accepted theory for planet formation <a href="https://faculty.ucr.edu/%7Ekrice/coreacc.html#:%7E:text=The%20most%20commonly%20accepted%20mechanism,to%20accrete%20a%20gaseous%20envelope.">is that of “core accretion”</a>. According to this model, tiny dust particles smaller than sand collide with each other, group together and progressively grow into larger and larger bodies. This is effectively what happens to the dust under your bed when it isn’t cleaned. </p>
<p>Once a core of dust with enough massive forms, it draws gas from the disc to form a gas giant planet. This bottom-to-top approach would take a few million years. </p>
<p>The opposite, top-to-bottom approach, is the <a href="https://blog.planethunters.org/tag/disk-instability/">theory of disc instability</a>. In this model, the protostellar discs that attend young stars are gravitationally unstable. In other words, they are too heavy to be maintained and so fragment into pieces, which evolve into planets. </p>
<p>The theory of core accretion has been around for a long time and it can explain many aspects of how our Solar System formed. However, disc instability can better explain some of the exoplanetary systems we have discovered in recent decades, such as those where a gas giant planet orbits very very far from its host star.</p>
<p>The appeal of this theory is that planet formation happens very fast, within a few thousand years, which is consistent with observations that suggest planets exist in very young discs.</p>
<p>Our study focused on gas giant planets formed via the model of disc instability. They are flattened because they form from the compression of an already flat structure, the protostellar disc, but also because of how they rotate. </p>
<h2>No flat Earths</h2>
<p>Although these protoplanets overall are very flattened, their cores, which will eventually evolve into gas giant planets as we know them, are less flattened – only by about 20%. This is just twice the flattening of Saturn. With time they are expected to become more spherical.</p>
<p>Rocky planets, like Earth and Mars, cannot form via disc instability. They are thought to form by slowly assembling dust particles to pebbles, rocks, kilometre-sized objects and eventually planets. They are too dense to be significantly flattened even when they are newly born. There is no possibility that Earth was flattened at such a high degree when it as young.</p>
<p>But our study does support a role for disc instability in the case of some worlds in some planetary systems.</p>
<p>We are now moving from the era of exoplanet discoveries to the era of exoplanet characterisation. Many new observatories are set to become operational. These will help discover more protoplanets embedded in their discs. Predictions from computer models are also becoming more sophisticated. </p>
<p>The comparison between these theoretical models and observations is bringing us closer and closer to understanding the origins of our Solar System.</p><img src="https://counter.theconversation.com/content/223247/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dimitris Stamatellos receives funding from the Science and Technology Facilities Council (STFC).</span></em></p>The observation could fill in gaps in our knowledge about planet formation.Dimitris Stamatellos, Associate Professor in Astrophysics, University of Central LancashireLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2156532024-02-11T13:50:28Z2024-02-11T13:50:28ZAn astronomer’s lament: Satellite megaconstellations are ruining space exploration<figure><img src="https://images.theconversation.com/files/574233/original/file-20240207-22-qbjsk9.jpg?ixlib=rb-1.1.0&rect=0%2C35%2C6000%2C3952&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Telescopes have to contend with light pollution from satellites.</span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><p>I used to love rocket launches when I was younger. During every launch, I imagined what it would feel like to be an astronaut sitting in the spacecraft, listening to that final countdown and then feeling multiple gees push me up through the atmosphere and away from our blue marble. </p>
<p>But as I learned more about the <a href="https://www.technologyreview.com/2018/06/22/142160/this-is-how-many-people-wed-have-to-send-to-proxima-centauri-to-make-sure-someone-actually/">severe limitations of human spaceflight</a>, I turned my attention to the oldest and most accessible form of space exploration: the science of astronomy.</p>
<p>Since 2019, I’ve watched my unencumbered enthusiasm for rocket launches soften to tepid interest, and finally sour to outright dread. <a href="https://globalnews.ca/news/9910084/the-new-space-race-2023/">The corporate space race</a>, led by SpaceX, is entirely responsible for this transformation in my mindset. </p>
<p>I am worried by the complete shift to the move-fast-and-break-things attitude that comes from the tech sector instead of government scientific agencies. I am put off by the <a href="https://press.uchicago.edu/ucp/books/book/chicago/A/bo184287883.html">colonialist language and billionaire-worship</a> of private corporations. I am increasingly furious at the <a href="https://www.startribune.com/string-lights-sky-not-ufo-starlink-satellite-internet/600324333/">nonexistent public education</a> and lack of transparency offered by these companies. </p>
<p>The final nail in the coffin for my love of rocket launches came with <a href="https://www.cnn.com/videos/business/2022/04/04/spacex-satellite-pollution-gothere-cnn-plus.cnn">SpaceX’s Starlink satellite megaconstellations</a>.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/soon-1-out-of-every-15-points-of-light-in-the-sky-will-be-a-satellite-170427">Soon, 1 out of every 15 points of light in the sky will be a satellite</a>
</strong>
</em>
</p>
<hr>
<h2>Crowded orbits</h2>
<p>The corporate space race is well underway, with private companies flooding Low Earth Orbit with <a href="https://planet4589.org/space/con/conlist.html">thousands of mass-produced satellites</a>. In previous decades, the prohibitively high cost of launch kept the rate of increase and total number of satellites from growing too rapidly. But launches have been getting steadily cheaper for years.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/OFfV33_eYPI?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Al Jazeera reports on the impacts of Starlink satellites.</span></figcaption>
</figure>
<p>SpaceX has launched thousands of their own Starlink communication satellites, as well as hundreds of satellites for their direct competitors. <a href="https://www.illdefined.space/2023-global-space-activity-dashboards/">Half of all launches worldwide in 2023</a> were SpaceX rockets. </p>
<p>As an astronomer, I’m painfully aware of what these thousands of new satellites have done to the night sky worldwide. They reflect sunlight long after the sky has grown dark, looking like moving stars. </p>
<p>Starlink satellites are the most numerous and occupy some of the lowest orbits, so they make up the majority of the satellites seen in the sky. </p>
<p>Last year, SpaceX launched one of the <a href="https://doi.org/10.1038/s41586-023-06672-7">brightest objects in the sky</a> on behalf of another company: BlueWalker 3, a satellite with the same sky-footprint as a small house. They plan to operate a fleet of dozens, <a href="https://rdcu.be/drQOU">each as bright</a> as the brightest stars in the sky.</p>
<h2>Lost information and knowledge</h2>
<p>These satellites are now increasingly obstructing telescopic space exploration, <a href="https://www.nytimes.com/2024/01/09/science/astronomy-telescopes-satellites-spacex-starlink.html">both on the ground</a> and <a href="https://doi.org/10.1038/s41550-023-01903-3">in space</a>. Astronomers are the canaries in the coal mine for this rapidly expanding experiment in orbit: we see these satellites increasingly affecting our research every day.</p>
<p>I have watched over the past five years as satellite streaks in my own research images from the <a href="https://www.cfht.hawaii.edu/">Canada-France-Hawaii Telescope</a> have changed from an unusual occurrence to lost data in nearly every image.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/568276/original/file-20240108-25-vkyhs5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="a series of grey boxes with white streaks" src="https://images.theconversation.com/files/568276/original/file-20240108-25-vkyhs5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/568276/original/file-20240108-25-vkyhs5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=491&fit=crop&dpr=1 600w, https://images.theconversation.com/files/568276/original/file-20240108-25-vkyhs5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=491&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/568276/original/file-20240108-25-vkyhs5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=491&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/568276/original/file-20240108-25-vkyhs5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=617&fit=crop&dpr=1 754w, https://images.theconversation.com/files/568276/original/file-20240108-25-vkyhs5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=617&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/568276/original/file-20240108-25-vkyhs5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=617&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 composite of 29 individual exposures from the Canada-France-Hawaii Telescope on Maunakea, taken in August 2022. The horizontal and diagonal white lines are bright satellites that unexpectedly flew through the field of view during observations, covering any objects behind them.</span>
<span class="attribution"><span class="source">(P. Cowan/W. Fraser/S. Lawler/CLASSY Survey Team/CFHT)</span></span>
</figcaption>
</figure>
<p>Astronomy is the only way to learn about the universe, the overwhelming majority of which can never be explored by humans. The farthest human-made object from Earth is the <a href="https://voyager.jpl.nasa.gov/mission/status/">Voyager 1 probe</a>, now eight times farther from the sun than Neptune after 46 years continuously travelling significantly faster than a speeding bullet. </p>
<p>But even if Voyager 1 was pointed directly toward our nearest neighbouring star, Proxima Centauri (it’s not), it would take over 100,000 years to get there. We are light-years away from having technology that can robotically explore even our neighbouring solar systems on a human timescale, let alone bring humans out to the stars.</p>
<p>The vast majority of astronomy research is carried out by telescopes on Earth: large optical telescopes on remote mountaintops, large radio telescopes in radio-quiet zones that are meticulously maintained, as well as smaller telescopes scattered around the world.</p>
<p>There are a handful of telescopes in Low Earth Orbit that also have to <a href="https://skyandtelescope.org/astronomy-news/satellite-trails-mar-hubble-images/">contend with light pollution</a> from Starlink and other megaconstellations. There are also a <a href="https://webb.nasa.gov/content/about/orbit.html">handful of telescopes outside Earth orbit</a> which can only operate for a few years, unlike ground-based facilities that can be maintained and enhanced with new technologies for decades.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/574239/original/file-20240207-28-qmjb00.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="a large white dome looms against a dark sky" src="https://images.theconversation.com/files/574239/original/file-20240207-28-qmjb00.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/574239/original/file-20240207-28-qmjb00.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/574239/original/file-20240207-28-qmjb00.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/574239/original/file-20240207-28-qmjb00.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/574239/original/file-20240207-28-qmjb00.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/574239/original/file-20240207-28-qmjb00.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/574239/original/file-20240207-28-qmjb00.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"></a>
<figcaption>
<span class="caption">The Canada-Hawaii-France telescope, located on the summit of Mauna Kea, a dormant volcano located on the island of Hawaii.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<h2>Government regulation needed</h2>
<p>Space exploration using Earth-based telescopes is growing increasingly less effective as more bright and radio-loud satellites are placed between Earth and the stars. But there are much worse problems ahead if corporations continue launching satellites: atmospheric pollution on launch and <a href="https://doi.org/10.1073/pnas.2313374120">reentry</a>, ground casualty risks from <a href="https://doi.org/10.1038/s41550-022-01718-8">reentries</a>, and the very real possibility of a <a href="https://doi.org/10.1038/s41598-021-89909-7">runaway collisional cascade in orbit</a>, referred to as the Kessler Syndrome.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/a-rapidly-growing-rocket-industry-could-undo-decades-of-work-to-save-the-ozone-layer-unless-we-act-now-198982">A rapidly growing rocket industry could undo decades of work to save the ozone layer – unless we act now</a>
</strong>
</em>
</p>
<hr>
<p>Satellites are an incredibly useful part of our lives, but there are limits to how many can safely orbit Earth. Current regulations on launches and orbital operations by governments are very weak, and are not set up for the current regime of thousands of new satellites per year. </p>
<p>Regulation on the number of satellites in orbit would force corporations toward technology improvements and service models that use fewer satellites, keeping orbit usable for future generations.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/its-not-too-late-to-save-the-night-sky-but-governments-need-to-get-serious-about-protecting-it-158394">It's not too late to save the night sky, but governments need to get serious about protecting it</a>
</strong>
</em>
</p>
<hr>
<p>Ask your government representatives to support <a href="https://www.asc-csa.gc.ca/eng/transparency/consultations/what-we-heard-consulting-canadians-modern-regulatory-framework-space.asp">satellite regulation</a>, and expansion of <a href="https://crtc.gc.ca/eng/internet/internet.htm">rural broadband</a>. Get out and enjoy your <a href="https://www.cleardarksky.com/maps/lp/large_light_pollution_map.html">dark skies</a>, before they change. </p>
<p>With proper regulation, our oldest form of space exploration can continue. I desperately hope we never reach a point where the natural patterns in the sky are drowned out by anthropogenic ones, but without regulation, corporations will get us there soon.</p><img src="https://counter.theconversation.com/content/215653/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Samantha Lawler receives research funding from the Natural Sciences and Engineering Research Council of Canada.</span></em></p>Megaconstellations of satellites are hindering the most powerful tool for space exploration: telescopes.Samantha Lawler, Associate professor, Astronomy, University of ReginaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2198922024-02-05T13:30:46Z2024-02-05T13:30:46ZUS Moon landing marks new active phase of lunar science, with commercial launches of landers that will study solar wind and peer into the universe’s dark ages<figure><img src="https://images.theconversation.com/files/567940/original/file-20240104-21-s3p58r.jpg?ixlib=rb-1.1.0&rect=4%2C17%2C2991%2C1868&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The dark, far side of the Moon is the perfect place to conduct radio astronomy. </span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/LunarEclipse/704e3da2df90473486270e23aa73419d/photo?Query=moon&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=399&digitizationType=Digitized&currentItemNo=12&vs=true&vs=true">AP Photo/Rick Bowmer</a></span></figcaption></figure><p>For the first time since 1972, NASA <a href="https://www.intuitivemachines.com/im-1">landed a craft on the surface of the Moon</a> in February 2024. But the agency didn’t do it alone – instead, it partnered with commercial companies. Thanks to new technologies and <a href="https://www.nasa.gov/commercial-lunar-payload-services/">public-private partnerships</a>, the scientific projects brought to the Moon on this craft and on future missions like it will open up new realms of scientific possibility. </p>
<p>As parts of several projects launching this year, teams of scientists, including myself, will conduct radio astronomy from the south pole and the far side of the Moon.</p>
<p>NASA’s <a href="https://www.nasa.gov/commercial-lunar-payload-services/">commercial lunar payload services program</a>, or CLPS, will use uncrewed landers to conduct NASA’s first science experiments from the Moon in over 50 years. The CLPS program differs from past space programs. Rather than NASA building the landers and operating the program, commercial companies will do so in a public-private partnership. NASA identified <a href="https://www.nasa.gov/commercial-lunar-payload-services/clps-providers/">about a dozen companies</a> to serve as vendors for landers that will go to the Moon. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/q3gePeT3yxg?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">CLPS will send science payloads to the Moon in conjunction with the Artemis program’s crewed missions.</span></figcaption>
</figure>
<p>NASA buys space on these landers for <a href="https://science.nasa.gov/lunar-science/clps-deliveries/">science payloads</a> to fly to the Moon, and the companies design, build and insure the landers, as well as contract with rocket companies for the launches. Unlike in the past, NASA is one of the customers and not the sole driver. </p>
<h2>Peregrine and Odysseus, the first CLPS landers</h2>
<p>The first two CLPS payloads are scheduled to launch during the first two months of 2024. There’s the <a href="https://science.nasa.gov/lunar-science/clps-deliveries/to2-astrobotic/">Astrobotics payload</a>, which launched Jan. 8 before its lander, named Peregrine, <a href="https://www.space.com/astrobotic-peregrine-moon-lander-headed-to-earth">experienced a fuel issue</a> that cut its journey to the Moon short. </p>
<p>Next, there’s the <a href="https://science.nasa.gov/lunar-science/clps-deliveries/op-to2-intuitive-machines/">Intuitive Machines payload</a>. Intuitive Machines’ lander, named Odysseus, <a href="https://www.intuitivemachines.com/im-1">landed near the south pole of the Moon</a> on Feb. 22, 2024. NASA has also planned a <a href="https://science.nasa.gov/lunar-science/clps-deliveries/">few additional landings</a> – about two or three per year – for each of the next few years.</p>
<p>I’m a <a href="https://www.colorado.edu/faculty/burns/">radio astronomer</a> and co-investigator on NASA’s <a href="https://www.colorado.edu/ness/projects/radiowave-observations-lunar-surface-photoelectron-sheath-rolses">ROLSES program</a>, otherwise known as Radiowave Observations at the Lunar Surface of the photoElectron Sheath. ROLSES was built by the NASA Goddard Space Flight Center and is led by <a href="https://science.gsfc.nasa.gov/sci/bio/natchimuthuk.gopalswamy-1">Natchimuthuk Gopalswamy</a>. </p>
<p>The ROLSES instrument landed on the Moon as <a href="https://www.intuitivemachines.com/_files/ugd/7c27f7_51f84ee63ea744a9b7312d17fefa9606.pdf">one of six NASA payloads</a> on the Intuitive Machines lander in February. Between ROLSES and another mission scheduled for the lunar far side in two years, LuSEE-Night, our teams will land NASA’s first two radio telescopes on the Moon by 2026. </p>
<h2>Radio telescopes on the Moon</h2>
<p>The Moon – particularly the far side of the Moon – is an ideal place to do radio astronomy and study signals from extraterrestrial objects such as the Sun and the Milky Way galaxy. On Earth, the ionosphere, which <a href="https://theconversation.com/earths-magnetic-field-protects-life-on-earth-from-radiation-but-it-can-move-and-the-magnetic-poles-can-even-flip-216231">contains Earth’s magnetic field</a>, distorts and absorbs radio signals below the <a href="https://www.fcc.gov/general/fm-radio">FM band</a>. These signals might get scrambled or may not even make it to the surface of the Earth.</p>
<p>On Earth, there are also TV signals, satellite broadcasts and defense radar systems <a href="https://theconversation.com/radio-interference-from-satellites-is-threatening-astronomy-a-proposed-zone-for-testing-new-technologies-could-head-off-the-problem-199353">making noise</a>. To do higher sensitivity observations, you have to go into space, away from Earth. </p>
<p>The Moon is what scientists call <a href="https://www.sciencefocus.com/space/what-is-tidal-locking">tidally locked</a>. One side of the Moon is always facing the Earth – the “<a href="https://www.rmg.co.uk/stories/topics/what-man-moon">man in the Moon</a>” side – and the other side, <a href="https://theconversation.com/whats-on-the-far-side-of-the-moon-111306">the far side</a>, always faces away from the Earth. The Moon has no ionosphere, and with about 2,000 miles of rock between the Earth and the far side of the Moon, there’s no interference. It’s radio quiet. </p>
<p>For our first mission with ROLSES, which launched in February 2024, we will collect data about environmental conditions on the Moon near its south pole. On the Moon’s surface, <a href="https://theconversation.com/solar-storms-can-destroy-satellites-with-ease-a-space-weather-expert-explains-the-science-177510">solar wind</a> directly strikes the lunar surface and creates a charged gas, called <a href="https://www.psfc.mit.edu/vision/what_is_plasma">a plasma</a>. Electrons lift off the negatively charged surface to form a highly ionized gas. </p>
<p>This doesn’t happen on Earth because <a href="https://theconversation.com/earths-magnetic-field-protects-life-on-earth-from-radiation-but-it-can-move-and-the-magnetic-poles-can-even-flip-216231">the magnetic field deflects</a> the solar wind. But there’s no global magnetic field on the Moon. With a low frequency radio telescope like ROLSES, we’ll be able to measure that plasma for the first time, which could help scientists figure out how to keep astronauts safe on the Moon. </p>
<p>When astronauts walk around on the surface of the Moon, they’ll pick up different charges. It’s like walking across the carpet with your socks on – when you reach for a doorknob, a spark can come out of your finger. The same kind of discharge happens on the Moon from the charged gas, but it’s potentially more harmful to astronauts. </p>
<h2>Solar and exoplanet radio emissions</h2>
<p>Our team is also going to use ROLSES to look at the Sun. The Sun’s surface releases shock waves that send out highly energetic particles and low radio frequency emissions. We’ll use the radio telescopes to measure these emissions and to see bursts of low-frequency radio waves from shock waves within the solar wind.</p>
<p>We’re also going to examine the Earth from the surface of the Moon and use that process as a template for <a href="https://theconversation.com/nasas-tess-spacecraft-is-finding-hundreds-of-exoplanets-and-is-poised-to-find-thousands-more-122104">looking at radio emissions from exoplanets</a> that may harbor life <a href="https://theconversation.com/are-there-any-planets-outside-of-our-solar-system-164062">in other star systems</a>. </p>
<p>Magnetic fields are important for life because they shield the planet’s surface from the <a href="https://theconversation.com/the-scorching-winds-on-the-surface-of-the-sun-and-how-were-forecasting-them-44098">solar/stellar wind</a>. </p>
<p>In the future, our team hopes to use specialized arrays of antennas on the far side of the Moon to observe nearby stellar systems that are known to have exoplanets. If we detect the same kind of radio emissions that come from Earth, this will tell us that the planet has a magnetic field. And we can measure the strength of the magnetic field to figure out whether it’s strong enough to shield life.</p>
<h2>Cosmology on the Moon</h2>
<p>The Lunar Surface Electromagnetic Experiment at Night, or <a href="https://www.colorado.edu/ness/projects/lunar-surface-electromagnetics-experiment-night-lusee-night">LuSEE-Night</a>, will fly in early 2026 to the far side of the Moon. LuSEE-Night marks scientists’ first attempt to do cosmology on the Moon.</p>
<p>LuSEE-Night is a novel collaboration between NASA and the Department of Energy. Data will be sent back to Earth using a communications satellite in lunar orbit, <a href="https://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration/A_pathway_for_communicating_at_the_Moon">Lunar Pathfinder</a>, which is funded by the European Space Agency.</p>
<p>Since the far side of the Moon is <a href="https://cosmicdawn.astro.ucla.edu/lunar_telescopes.html">uniquely radio quiet</a>, it’s the best place to do cosmological observations. During the two weeks of lunar night that happen every 14 days, there’s no emission coming from the Sun, and there’s no ionosphere. </p>
<p>We hope to study an unexplored part of the early universe called the <a href="https://www.astronomy.com/science/the-beginning-to-the-end-of-the-universe-the-cosmic-dark-ages/">dark ages</a>. The dark ages refer to before and just after the formation of the very first stars and galaxies in the universe, which is beyond what the <a href="https://webb.nasa.gov/">James Webb Space Telescope</a> can study.</p>
<p>During the dark ages, the universe was less than 100 million years old – today the universe is 13.7 billion years old. The universe was full of hydrogen <a href="https://theconversation.com/after-our-universes-cosmic-dawn-what-happened-to-all-its-original-hydrogen-65527">during the dark ages</a>. That hydrogen radiates through the universe at low radio frequencies, and when new stars turn on, they ionize the hydrogen, producing a radio signature in the spectrum. Our team hopes to measure that signal and learn about how the earliest stars and galaxies in the universe formed.</p>
<p>There’s also a lot of potential new physics that we can study in this last unexplored cosmological epoch in the universe. We will investigate the nature of <a href="https://theconversation.com/dark-matter-the-mystery-substance-physics-still-cant-identify-that-makes-up-the-majority-of-our-universe-85808">dark matter</a> and early <a href="https://theconversation.com/explainer-the-mysterious-dark-energy-that-speeds-the-universes-rate-of-expansion-40224">dark energy</a> and test our fundamental models of physics and cosmology in an unexplored age.</p>
<p>That process is going to start in 2026 with the LuSEE-Night mission, which is both a fundamental physics experiment and a cosmology experiment.</p>
<p><em>This is an updated version of an article originally published on Feb. 5, 2024.</em></p><img src="https://counter.theconversation.com/content/219892/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jack Burns receives funding from NASA.</span></em></p>Projects under NASA’s CLPS program – including the Odysseus lander that made it to the lunar surface – will probe unexplored questions about the universe’s formation.Jack Burns, Professor of Astrophysical and Planetary Sciences, University of Colorado BoulderLicensed as Creative Commons – attribution, no derivatives.