tag:theconversation.com,2011:/au/topics/red-giants-2040/articlesRed Giants – The Conversation2023-06-28T20:04:03Ztag:theconversation.com,2011:article/2086492023-06-28T20:04:03Z2023-06-28T20:04:03ZAstronomers puzzled by ‘planet that shouldn’t exist’<figure><img src="https://images.theconversation.com/files/534458/original/file-20230627-17-bpm2lk.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C1920%2C1080&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Julian Baum</span></span></figcaption></figure><p>The search for planets outside our Solar System – exoplanets – is one of the most rapidly growing fields in astronomy. Over the past few decades, more than 5,000 exoplanets have been detected and astronomers now estimate that on average there is at least one planet per star in our galaxy.</p>
<p>Many current research efforts aim at detecting Earth-like planets suitable for life. These endeavours focus on so-called “main sequence” stars like our Sun – stars which are powered by fusing hydrogen atoms into helium in their cores, and remain stable for billions of years. More than 90% of all known exoplanets so far have been detected around main-sequence stars.</p>
<p>As part of an international team of astronomers, we studied a star that looks much like our Sun will in billions of years’ time, and found it has a planet which by all rights it should have devoured. In <a href="https://www.nature.com/articles/s41586-023-06029-0">research</a> published today in Nature, we lay out the puzzle of this planet’s existence – and propose some possible solutions.</p>
<h2>A glimpse into our future: red giant stars</h2>
<p>Just like humans, stars undergo changes as they age. Once a star has used up all its hydrogen in the core, the core of the star shrinks and the outer envelope expands as the star cools. </p>
<p>In this “red giant” phase of evolution, stars can grow to more than 100 times their original size. When this happens to our Sun, in about 5 billion years, we expect it will grow so large it will engulf Mercury, Venus, and possibly Earth.</p>
<p>Eventually, the core becomes hot enough for the star to begin fusing helium. At this stage the star shrinks back to about 10 times its original size, and continues stable burning for tens of millions of years.</p>
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Read more:
<a href="https://theconversation.com/explainer-how-do-you-find-exoplanets-24153">Explainer: how do you find exoplanets?</a>
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<p>We know of hundreds of planets orbiting red giant stars. One of these is called <a href="https://exoplanets.nasa.gov/exoplanet-catalog/7100/8-ursae-minoris-b/">8 Ursae Minoris b</a>, a planet with around the mass of Jupiter in an orbit that keeps it only about half as far from its star as Earth is from the Sun.</p>
<p>The planet was discovered in 2015 by a team of Korean astronomers using the “Doppler wobble” technique, which measures the gravitational pull of the planet on the star. In 2019, the International Astronomical Union <a href="https://www.nameexoworlds.iau.org/_files/ugd/6358ac_5eebee4eba4f41b7a9f6201123673a24.pdf">dubbed</a> the star Baekdu and the planet Halla, after the tallest mountains on the Korean peninsula.</p>
<h2>A planet that should not be there</h2>
<p>Analysis of new data about Baekdu collected by NASA’s Transiting Exoplanet Survey Satellite (<a href="https://www.nasa.gov/tess-transiting-exoplanet-survey-satellite/">TESS</a>) space telescope has yielded a surprising discovery. Unlike other red giants we have found hosting exoplanets on close-in orbits, Baekdu has already started fusing helium in its core.</p>
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Read more:
<a href="https://theconversation.com/nasas-planet-hunting-spacecraft-tess-is-now-on-its-mission-to-search-for-new-worlds-94291">NASA's planet-hunting spacecraft TESS is now on its mission to search for new worlds</a>
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<p>Using the techniques of <a href="https://exoplanets.nasa.gov/news/1516/symphony-of-stars-the-science-of-stellar-sound-waves/">asteroseismology, which studies waves inside stars</a>, we can determine what material a star is burning. For Baekdu, the frequencies of the waves unambiguously showed it has commenced burning helium in its core.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/534474/original/file-20230628-19-njdov.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/534474/original/file-20230628-19-njdov.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/534474/original/file-20230628-19-njdov.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=331&fit=crop&dpr=1 600w, https://images.theconversation.com/files/534474/original/file-20230628-19-njdov.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=331&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/534474/original/file-20230628-19-njdov.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=331&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/534474/original/file-20230628-19-njdov.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=416&fit=crop&dpr=1 754w, https://images.theconversation.com/files/534474/original/file-20230628-19-njdov.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=416&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/534474/original/file-20230628-19-njdov.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=416&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Sound waves inside a star can be used to determine whether it is burning helium.</span>
<span class="attribution"><span class="source">Gabriel Perez Diaz / Instituto de Astrofisica de Canarias</span></span>
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<p>The discovery was puzzling: if Baekdu is burning helium, it should have been much bigger in the past – so big it should have engulfed the planet Halla. How is it possible Halla survived?</p>
<p>As is often the case in scientific research, the first course of action was to rule out the most trivial explanation: that Halla never really existed. </p>
<p>Indeed, some apparent discoveries of planets orbiting red giants using the Doppler wobble technique have later been shown to be illusions <a href="https://ui.adsabs.harvard.edu/abs/2018AJ....155..120H/abstract">created by long-term variations in the behaviour of the star itself</a>. </p>
<p>However, follow-up observations ruled out such a false-positive scenario for Halla. The Doppler signal from Baekdu has remained stable over the last 13 years, and close study of other indicators showed no other possible explanation for the signal. Halla is real – which returns us to the question of how it survived engulfment. </p>
<h2>Two stars become one: a possible survival scenario</h2>
<p>Having confirmed the existence of the planet, we arrived at two scenarios which could explain the situation we see with Baekdu and Halla. </p>
<p>At least half of all stars in our galaxy did not form in isolation like our Sun, but are part of binary systems. If Baekdu once was a binary star, Halla may have never faced the danger of engulfment. </p>
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<img alt="" src="https://images.theconversation.com/files/534475/original/file-20230628-23-52qepf.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/534475/original/file-20230628-23-52qepf.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=509&fit=crop&dpr=1 600w, https://images.theconversation.com/files/534475/original/file-20230628-23-52qepf.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=509&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/534475/original/file-20230628-23-52qepf.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=509&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/534475/original/file-20230628-23-52qepf.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=640&fit=crop&dpr=1 754w, https://images.theconversation.com/files/534475/original/file-20230628-23-52qepf.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=640&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/534475/original/file-20230628-23-52qepf.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=640&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">If the star Baekdu used to be a binary, there are two scenarios which can explain the survival of the planet Halla.</span>
<span class="attribution"><span class="source">Brooks G. Bays, Jr, SOEST/University of Hawai'i</span></span>
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<p>A merger of these two stars may have prevented the expansion of either star to a size large enough to engulf planet Halla. If one star became a red giant on its own, it would have engulfed Halla – however, if it merged with a companion star it would jump straight to the helium-burning phase without getting big enough to reach the planet. </p>
<p>Alternatively, Halla may be a relatively newborn planet. The violent collision between the two stars may have produced a cloud of gas and dust from which the planet could have formed. In other words, the planet Halla may be a recently born “second generation” planet. </p>
<p>Whichever explanation is correct, the discovery of a close-in planet orbiting a helium-burning red giant star demonstrates that nature finds ways for exoplanets to appear in places where we might least expect them. </p>
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<a href="https://images.theconversation.com/files/534470/original/file-20230627-35262-ufsunt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An illustration of a planet in a ring of dust and debris around a star." src="https://images.theconversation.com/files/534470/original/file-20230627-35262-ufsunt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/534470/original/file-20230627-35262-ufsunt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/534470/original/file-20230627-35262-ufsunt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/534470/original/file-20230627-35262-ufsunt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/534470/original/file-20230627-35262-ufsunt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/534470/original/file-20230627-35262-ufsunt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/534470/original/file-20230627-35262-ufsunt.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>
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<span class="caption">The planet Halla may have formed from debris created by the merger of two stars.</span>
<span class="attribution"><span class="source">W. M. Keck Observatory / Adam Makarenko</span></span>
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</figure><img src="https://counter.theconversation.com/content/208649/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Daniel Huber receives funding from the Australian Research Council (ARC), the National Aeronautics and Space Administration (NASA), the National Science Foundation (NSF), and the Sloan Foundation. He is also affiliated with the University of Hawaiʻi. </span></em></p>The planet Halla looks like it should have been devoured by its host star, a red giant called Baekdu – but a secret in the star’s past may hold the answer to the planet’s present.Daniel Huber, Astronomer, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1696312021-10-13T19:12:52Z2021-10-13T19:12:52ZA distant dead star shows a glimpse of our Solar System’s future<figure><img src="https://images.theconversation.com/files/425917/original/file-20211012-27-16co7nu.jpg?ixlib=rb-1.1.0&rect=0%2C5%2C3952%2C2419&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Artist's rendition of the Jupiter-like planet and its white dwarf star</span> <span class="attribution"><span class="source">W. M. Keck Observatory/Adam Makarenko</span></span></figcaption></figure><p>The golden age of discovery of planets around other stars (known as exoplanets) began in 1995. Since the first discoveries, more than 4,500 worlds have been found, most of them orbiting ordinary stars like our Sun. </p>
<p>The Sun is about 4.6 billion years old, and Earth and all the other planets formed at about the same time. But what will happen to the planets in another 5 billion years, when the Sun eventually dies? </p>
<p>In <a href="https://www.nature.com/articles/s41586-021-03869-6">a new study published in Nature</a>, we show a glimpse of the possible future of our Solar System, when the Sun burns through all its hydrogen fuel and becomes a dead star called a white dwarf.</p>
<p>This possible future is depicted in the form of a white dwarf thousands of light years away, which hosts a gas giant planet on a similar orbit to Jupiter, between 2.5 and 6 times as far from its star as Earth is from the Sun.</p>
<h2>Magnifying gravity</h2>
<p>The journey to this discovery began in 2010, when the white dwarf and its Jupiter-like companion aligned perfectly with a much more distant star in the dense star fields at the centre of the Milky Way. </p>
<p>The gravity of the white dwarf and its companion acted like a magnifying glass, bending the light from the distant star and making it appear brighter to observers here on Earth. This effect, known as “gravitational microlensing”, was predicted by Einstein in 1936.</p>
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Read more:
<a href="https://theconversation.com/how-we-found-a-white-dwarf-a-stellar-corpse-by-accident-114089">How we found a white dwarf – a stellar corpse – by accident</a>
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<p>While the background star was magnified, the small scale of this chance event meant we could not distinguish between the star in the foreground and the star in the background, let alone the planet.</p>
<p>But details in how the magnification of the background star changes over time can be used to reveal properties of the closer star and its planet. So an international team of astronomers led by those from the University of Tasmania and NASA Goddard headed to Hawai’i to use one of the largest telescopes in the world for a better look.</p>
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<img alt="" src="https://images.theconversation.com/files/425925/original/file-20211012-25-6hym0o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/425925/original/file-20211012-25-6hym0o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/425925/original/file-20211012-25-6hym0o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/425925/original/file-20211012-25-6hym0o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/425925/original/file-20211012-25-6hym0o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/425925/original/file-20211012-25-6hym0o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/425925/original/file-20211012-25-6hym0o.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">
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<span class="caption">The twin Keck telescopes of Mauna Kea, Hawai'i.</span>
<span class="attribution"><span class="source">Joshua Blackman</span></span>
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<p>The Keck-II telescope atop the dormant Mauna Kea volcano has a 10-metre interlocking array of hexagonal mirrors and “laser-guided adaptive optics” to filter out “twinkling” caused by changes in the atmosphere. We used it to obtain extremely high-resolution images of both the background and foreground star.</p>
<p>To our surprise, however, we could not see the foreground star at all. Predictions from the original magnification event in 2010 indicated that this star, weighing about half as much as the Sun, should be visible. But we could not detect it.</p>
<p>After a few years grappling with our data to ensure we weren’t making a mistake, we realised we could not see the star because it is a white dwarf, which in this case was too faint to detect.</p>
<h2>Dead stars</h2>
<p>White dwarfs are Earth-sized remnants of ordinary stars like our Sun. About 95% of the stars in the Milky Way will eventually become white dwarfs.</p>
<p>In about 5 billion years’ time, when the Sun burns through all its hydrogen fuel, it will balloon in size to become a red giant, likely obliterating Mercury and Venus in the process. Earth may also be destroyed, or at least severely disrupted; if by some miracle humankind still exists by then, our distant descendants will have to move off-world to survive.</p>
<p>In the red giant phase, the Sun can delay its inevitable collapse by burning heavier atoms such as helium. However, this reprieve will last only 100 million years or so. </p>
<p>When these heavier fuels run out, the Sun will collapse into its final white dwarf state. In the collapse, the Sun will blow off about half its mass as a cloud of hot gas and push the surviving planets into a wider orbit.</p>
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<span class="caption">An artist’s rendition of the system.</span>
<span class="attribution"><span class="source">W. M. Keck Observatory/Adam Makarenko</span></span>
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<p>For the planets, there is a fine balancing act between being swallowed up during the expansion of the red giant and possibly being ejected into deep space when the white dwarf forms. Our discovery shows what some theorists have predicted: that planets at wide enough orbits are likely to survive the death of their host star. </p>
<p>Because most stars end up as white dwarfs, we don’t have a very precise estimate of what this system looked like when it formed. However, the statistics favour an origin as a star not too different in mass from the Sun. </p>
<p>The Universe isn’t old enough for stars smaller than about 80% as big as the Sun to have evolved into white dwarfs, and stars more than about twice the size of the Sun are intrinsically rare and also more likely to experience more turbulent deaths that would destroy their planetary systems. </p>
<p>Using the Hubble Space Telescope or its successor, the James Webb Space Telescope (due to launch in December 2021), we hope to learn more about the system by directly measuring the incredibly faint residual light emitted by this dead sun.</p>
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Read more:
<a href="https://theconversation.com/james-webb-space-telescope-an-astronomer-on-the-team-explains-how-to-send-a-giant-telescope-to-space-and-why-167516">James Webb Space Telescope: An astronomer on the team explains how to send a giant telescope to space – and why</a>
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<img src="https://counter.theconversation.com/content/169631/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Joshua Blackman receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Andrew A. Cole receives funding from the Australian Research Council. </span></em></p>In 5 billion years the Sun will collapse. A new discovery suggest some planets may still survive afterwards.Joshua W. Blackman, Astronomer, University of TasmaniaAndrew A. Cole, Associate Professor in Astrophysics, University of TasmaniaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1140892019-04-30T03:34:26Z2019-04-30T03:34:26ZHow we found a white dwarf – a stellar corpse – by accident<figure><img src="https://images.theconversation.com/files/270571/original/file-20190423-175548-g8mn17.jpg?ixlib=rb-1.1.0&rect=122%2C6%2C1818%2C1020&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Searching for planets around nearby stars is like searching for a needle in a field of haystacks. </span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/trevor_dobson_inefekt69/25626842713">Trevor Dobson/Flikr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>One of the great things about science is that, when you start to observe a new object in space, you can never be sure quite what you’ll find. </p>
<p>We received a fantastic reminder of this during observations designed to check whether nearby stars had planetary companions. Our observations confirmed the discovery of a couple of planets, but also yielded an unexpected surprise.</p>
<p>Buried among our candidates was the corpse of a star – <a href="http://astronomy.swin.edu.au/cosmos/W/White+Dwarf">a white dwarf</a> – a discovery we announced this month in <a href="https://doi.org/10.3847/1538-4357/ab0e74" title="Discovery of a Compact Companion to a Nearby Star">The Astrophysical Journal</a>.</p>
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Read more:
<a href="https://theconversation.com/why-pluto-is-losing-its-atmosphere-winter-is-coming-115567">Why Pluto is losing its atmosphere: winter is coming</a>
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<h2>The search for stellar wobbles</h2>
<p>Our story begins with a survey called the Anglo-Australian Planet Search (<a href="http://newt.phys.unsw.edu.au/%7Ecgt/planet/AAPS_Home.html">AAPS</a>), which spent 17 years looking for alien worlds using the 3.9-metre <a href="https://www.aao.gov.au/about-us/anglo-australian-telescope">Anglo-Australian Telescope</a> at <a href="https://www.sidingspringobservatory.com.au/">Siding Spring Observatory</a> in New South Wales.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/270197/original/file-20190421-1403-1xhz7ak.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/270197/original/file-20190421-1403-1xhz7ak.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/270197/original/file-20190421-1403-1xhz7ak.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/270197/original/file-20190421-1403-1xhz7ak.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/270197/original/file-20190421-1403-1xhz7ak.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/270197/original/file-20190421-1403-1xhz7ak.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/270197/original/file-20190421-1403-1xhz7ak.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/270197/original/file-20190421-1403-1xhz7ak.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 Anglo-Australian Telescope, at Siding Spring Observatory, offers spectacular views of the southern sky.</span>
<span class="attribution"><span class="source">Jonti Horner</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>We often say a planet orbits a star (Earth orbits the Sun, for example), but the truth is slightly more complicated. Instead, the two orbit around their common centre of mass. As a result, a star that hosts a planet will wobble, rocking back and forth over time.</p>
<p><a href="https://theconversation.com/explainer-how-to-find-an-exoplanet-part-1-56682">Radial velocity surveys</a> search for planets by attempting to detect that telltale wobble. Over its lifetime, the AAPS discovered more than 40 planets in this manner. </p>
<p>But it is almost certain that more planets remained undiscovered in the AAPS data. So we began searching for those hidden worlds.</p>
<p>In several cases we found stars that exhibited distinct signs of a wobble, but for which less than a full orbit had been completed. Without observing a full orbit, we don’t know whether the companions causing the wobble are planets, or other stars.</p>
<p>So how can we work out what we’ve found?</p>
<h2>Direct imaging – a new trick</h2>
<p>We identified 21 stars around which there could be a planet, but to be sure, we needed more data. Unfortunately, the AAPS had ended, so we needed to do something innovative.</p>
<p>For each of our stars, there were two possibilities: either the wobble is caused by a planet, or by something bigger (such as a <a href="http://coolcosmos.ipac.caltech.edu/cosmic_classroom/cosmic_reference/brown_dwarfs.html">brown dwarf</a> or <a href="https://www.atnf.csiro.au/outreach/education/senior/astrophysics/binary_types.html">an unseen stellar companion</a>).</p>
<p>Recent advances in astronomical imaging techniques mean we can now use the world’s largest telescopes to look at nearby stars and see objects very close to them – closer than has ever been possible before. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/QIadRr0QX_Q?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Astronomical imaging showing the four giant planets orbiting HR 8799.</span></figcaption>
</figure>
<p>We used the <a href="https://www.gemini.edu/sciops/telescopes-and-sites">8.1m Gemini-South telescope</a> in Chile to obtain high-resolution images of our target stars, to see whether we could see any previously hidden companions. </p>
<p>Despite the power of the technique, any planets around our targets would remain invisible. But if the observed wobbles were caused by more massive objects, we should be able to see those objects and hence rule out the planetary hypothesis.</p>
<h2>The peculiar case of HD 118473</h2>
<p>For 20 of our targets, things went as we expected. In some cases, we detected a previously undiscovered stellar companion. In others, we could rule out massive companions, giving us confidence in the presence of planets around those stars.</p>
<p>But for one star, things got weird. On the basis of the wobble data, we knew that the <em>lowest possible mass</em> the companion could have is around 0.44 times the mass of the Sun. That’s <a href="http://blogs.discovermagazine.com/outthere/2017/08/04/how-big-is-the-biggest-possible-planet/">much too massive to be a planet</a>.</p>
<p>With that much mass, we would <a href="https://slate.com/technology/2014/06/the-brown-dwarf-limit-astronomers-have-found-the-smallest-star-known.html">expect the companion to be a star</a>, fainter and cooler than the Sun, but easily visible with Gemini-South.</p>
<p>But when we looked at our images, no companion star was visible.</p>
<h2>A macabre twist</h2>
<p>The radial velocity data is clear – there is a massive companion orbiting HD118473, causing that star to wobble back and forth with a period of 5.67 years.</p>
<p>But it can’t be a planet (it’s far too massive), and it can’t be a star (we’d be able to see it). So what could it be?</p>
<p>The answer comes down to the way stars live and die.</p>
<p>Vast as stars are, their supply of fuel is not unlimited. Eventually the fuel runs out and the end of the star’s life is imminent. The more massive the star, the more spectacular that end will be.</p>
<p>A star like the Sun <a href="https://theconversation.com/curious-kids-whats-going-to-happen-to-the-sun-in-the-future-will-it-explode-78029">will eventually swell to become a red giant</a>, then will puff off its outer layers, creating a spectacular planetary nebula, and leaving behind a glowing ember – its core, bare and exposed to space.</p>
<p>That core is a <a href="http://astronomy.swin.edu.au/cosmos/W/White+Dwarf">white dwarf</a> – around the size of Earth, but with the mass of a star. Tiny, compared with the star from which it came, the white dwarf gradually cools and fades to obscurity over billions of years.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/270572/original/file-20190423-175528-curwg7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/270572/original/file-20190423-175528-curwg7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/270572/original/file-20190423-175528-curwg7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/270572/original/file-20190423-175528-curwg7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/270572/original/file-20190423-175528-curwg7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/270572/original/file-20190423-175528-curwg7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/270572/original/file-20190423-175528-curwg7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/270572/original/file-20190423-175528-curwg7.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"></a>
<figcaption>
<span class="caption">Artist’s impression of Sirius B, the closest known white dwarf.</span>
<span class="attribution"><span class="source">NASA, ESA and G. Bacon (STScI)</span></span>
</figcaption>
</figure>
<p>More massive stars die violently – as <a href="http://astronomy.swin.edu.au/cosmos/s/supernova">supernovae</a> that outshine whole galaxies. But they also leave behind corpses that are faint and hard to spot. <a href="http://astronomy.swin.edu.au/cosmos/n/neutron+star">Neutron stars</a> – the size of a city, but with a mass greater than the Sun – and <a href="http://astronomy.swin.edu.au/cosmos/B/Black+Hole">black holes</a> – tiny and invisible, except when they’re devouring something.</p>
<p>All this brings us back to our hidden companion to HD118473 – the mass of a star, but too faint to see. What could it be?</p>
<h2>An unexpected ancient relic</h2>
<p>By far the most likely answer is that the hidden companion is a white dwarf. In the distant past, HD118473 was a <a href="http://astronomy.swin.edu.au/cosmos/b/binary+star">binary star</a> with the two components shining bright as they orbited their common centre of mass.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/observing-the-invisible-the-long-journey-to-the-first-image-of-a-black-hole-115064">Observing the invisible: the long journey to the first image of a black hole</a>
</strong>
</em>
</p>
<hr>
<p>For a few billion years, nothing changed, until the more massive of the stars reached the end of its life. It swelled to become a <a href="http://astronomy.swin.edu.au/cosmos/R/Red+giant+stars">red giant</a> then shed its outer layers, leaving behind a white dwarf, too dim for us to detect.</p>
<p>The white dwarf’s companion continues through space as we speak, still whirling in a celestial waltz with what remains of its companion. A dim, hidden relic to deceive exoplanet hunters, and a reminder of how science always has another surprise waiting around the corner.</p><img src="https://counter.theconversation.com/content/114089/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>Science is full of surprises. While searching for planets orbiting nearby stars, researchers stumbled across the remains of a star that once outshone the Sun.Jonti Horner, Professor (Astrophysics), University of Southern QueenslandStephen Kane, Associate Professor, University of California, RiversideLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1153292019-04-15T12:03:35Z2019-04-15T12:03:35ZCurious Kids: what would happen if the sun exploded?<figure><img src="https://images.theconversation.com/files/269294/original/file-20190415-147499-7uzj0m.jpg?ixlib=rb-1.1.0&rect=35%2C17%2C5955%2C4760&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">What's left after a star explodes. </span> <span class="attribution"><a class="source" href="https://upload.wikimedia.org/wikipedia/commons/d/d4/Keplers_supernova.jpg">NASA/ESA/JHU/R.Sankrit & W.Blair via Wikimedia Commons. </a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&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="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p><em><a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a> is a series by <a href="https://theconversation.com/uk">The Conversation</a>, which gives children of all ages the chance to have their questions about the world answered by experts. All questions are welcome: send them – along with your name, age and the town or city where you live – to curiouskids@theconversation.com. We won’t be able to answer every question, but we’ll do our best.</em></p>
<hr>
<blockquote>
<p><strong><em>What would happen if the sun exploded? – Lizey, aged 12, Australia.</em></strong></p>
</blockquote>
<p>The sun is a star, and when a star explodes it’s called <a href="https://www.esa.int/kids/en/learn/Our_Universe/Stars_and_galaxies/Supernovas">a supernova</a>. These types of explosions are very bright, and very powerful. They release lots of dust into space, which is used to make more stars and planets. Our solar system was made using stuff from these explosions. Even humans are <a href="https://www.youtube.com/watch?v=tLPkpBN6bEI">made of star stuff</a>! </p>
<p>If the sun suddenly exploded like this, the whole solar system would be destroyed. You don’t have to worry though – only stars ten times the size of our sun, or bigger, can explode like this. Our sun will end its life in a different way. </p>
<p>A supernova is like bursting a balloon. But when our sun dies, it will happen slowly, like when you gradually let the air out of a balloon.</p>
<h2>The death of the sun</h2>
<p>The sun will start to die when it runs out of fuel in <a href="http://thescienceexplorer.com/universe/what-will-happen-when-sun-eventually-dies">about 5,000,000,000 years</a> (that’s five billion years). This is 77 times longer than the Tyrannosaurus-Rex has been extinct … a very, very long time. </p>
<p>When the sun starts to die, it will get bigger and slightly colder, turning into what astronomers call a “red giant”. It will get so big, that it will eat Mercury, Venus and even Earth. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/269298/original/file-20190415-147480-1ae7x5u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/269298/original/file-20190415-147480-1ae7x5u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=375&fit=crop&dpr=1 600w, https://images.theconversation.com/files/269298/original/file-20190415-147480-1ae7x5u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=375&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/269298/original/file-20190415-147480-1ae7x5u.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=375&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/269298/original/file-20190415-147480-1ae7x5u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=471&fit=crop&dpr=1 754w, https://images.theconversation.com/files/269298/original/file-20190415-147480-1ae7x5u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=471&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/269298/original/file-20190415-147480-1ae7x5u.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=471&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Earth could be in big trouble.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/solar-system-sun-red-giant-star-1039317385?src=Sl-qDevfHdfgoqMHTlyAyA-1-7">Shutterstock.</a></span>
</figcaption>
</figure>
<p>When the sun is a red giant, it will be big and puffy, and start to blow off its outer layers out of the solar system. It will get smaller and smaller, eventually becoming what we then call a white dwarf. </p>
<h2>The sun as a white dwarf</h2>
<p>A white dwarf is the core of a dead star. They are super heavy, weighing almost as much as the sun, while being only the size of the Earth. A teaspoon of white dwarf would weigh <a href="https://www.nasa.gov/topics/universe/features/whitedwarf_pulsar.html">somewhere around 6,000 kilograms</a> – as much as an adult elephant!</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/qsN1LglrX9s?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>When the sun is a white dwarf, most of the solar system will still be around. Mercury, Venus and Earth will be gone, but Mars, Jupiter, Saturn, Uranus and Neptune will survive and continue to go around the sun. So will the asteroid belt, Kuiper belt and dwarf planets like Pluto. </p>
<p>Because a white dwarf is small, it doesn’t produce as much light. A white dwarf doesn’t have any fuel to give it energy, so it also gets colder and colder over time. Eventually it will become very dark.</p>
<h2>Life after the sun</h2>
<p>The light from the sun is what keeps our planet warm. Without it, the planets in the solar system will get very cold. This would make it harder for life to stay alive in the solar system. </p>
<p>A white dwarf doesn’t produce much light. But in the future, humans might build spaceships that will allow us to leave Earth. Humans might even build something to move the Earth. This would let the planet survive being eaten by the sun as a red giant. </p>
<p>The sun will become a red giant and then a white dwarf over billions of years. This is a very long time. We cannot watch a star do all of this, but we can learn how stars are born and die by looking at the stars in our galaxy - the Milky Way. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-fate-of-the-earth-we-discovered-the-remains-of-a-planet-following-the-violent-death-of-its-parent-star-114848">The fate of the Earth? We discovered the remains of a planet following the violent death of its parent star</a>
</strong>
</em>
</p>
<hr>
<p>The Milky Way has stars of all ages, and over time astronomers have worked out which ones are young, old or dead. By <a href="https://theconversation.com/the-fate-of-the-earth-we-discovered-the-remains-of-a-planet-following-the-violent-death-of-its-parent-star-114848">studying the old and dead stars</a>, we can discover what will happen to our sun in the far, far future.</p>
<hr>
<p><em>More <a href="https://theconversation.com/topics/curious-kids-36782?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">Curious Kids</a> articles, written by academic experts:</em></p>
<ul>
<li><p><em><a href="https://theconversation.com/curious-kids-is-water-blue-or-is-it-just-reflecting-off-the-sky-113199?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">Is water blue or is it just reflecting off the sky? – The students of Ms Brown’s class, Neerim South Public School, Victoria, Australia</a></em></p></li>
<li><p><em><a href="https://theconversation.com/curious-kids-who-is-siri-114940?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">Who is Siri? – Miles, aged four, London, UK.</a></em></p></li>
<li><p><em><a href="https://theconversation.com/curious-kids-how-did-the-months-get-their-names-113558?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">How did the months get their names? - Sylvie, aged eight, Brisbane, Australia.</a></em></p></li>
</ul><img src="https://counter.theconversation.com/content/115329/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Christopher Manser 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>By studying old and dead stars, we can discover what will happen to our sun in the far, far future. And it won’t end with a big explosion.Christopher Manser, Postdoctoral Researcher of Astrophysics, University of WarwickLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/495202015-10-21T17:03:07Z2015-10-21T17:03:07ZDead star demolishes planet – offering a glimpse into how the Earth could end its days<figure><img src="https://images.theconversation.com/files/99158/original/image-20151021-15449-1aur6ac.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A disintergating asteroid caught in the gravitational pull of a white dwarf star: could this be the future fate of the Earth?</span> <span class="attribution"><span class="source">Mark A. Garlick </span></span></figcaption></figure><p>Astronomers have made <a href="http://nature.com/articles/doi:10.1038/nature15527">the first direct discovery</a> of a <a href="http://science.nationalgeographic.com/science/space/universe/white-dwarfs-article/">white dwarf star</a> being orbited by a disintegrating minor planet that will ultimately collide into it. The observation, made by the <a href="http://kepler.nasa.gov/">Kepler space telescope</a>, offers a glimpse into what could happen to the Earth in a few billion years as the Sun, like most stars, becomes a white dwarf.</p>
<p>The study, published in <a href="http://www.nature.com/">Nature</a>, also adds to a growing number of studies reporting that dwarf stars can have atmospheres polluted with heavy elements – in some cases the constituents of water. Knowing that planets can be the source of such contamination gives weight to a hypothesis that says water on Earth was <a href="https://theconversation.com/watery-asteroid-gobbled-up-by-a-white-dwarf-implications-for-life-18987">deposited by rocky bodies</a> from distant regions in our solar system.</p>
<h2>Strange pollution</h2>
<p>Most stars, including our Sun, will <a href="http://science.nationalgeographic.com/science/space/universe/white-dwarfs-article/">become white dwarfs</a> as they die – before going out as a black dwarf or supernova – when they have exhausted their nuclear fuel. Our standard model for white dwarfs would predict white dwarfs to have no elements heavier than helium in the atmosphere, but a growing number of measurements of white dwarf atmospheres show the <a href="https://theconversation.com/polluted-dwarf-star-could-hold-the-key-to-the-origin-of-water-on-earth-41468">presence of heavier elements</a> such as oxygen, magnesium, silicon and iron. This is surprising because the star’s strong surface gravity is expected to cause heavy elements to sink quickly to the centre – leaving simple atmospheres of hydrogen and helium. </p>
<p>One explanation for this atmospheric pollution is that rocky bodies with similar properties to those in our solar system collide with a white dwarf and replenish its atmosphere with new heavy elements, including water. However, until now, there was no direct evidence that such rocky bodies exist or could fall onto a white dwarf. </p>
<p>The authors of the new study discovered the planet by noticing a dip in the brightness – a transit-like signal – from the white dwarf <a href="http://simbad.u-strasbg.fr/simbad/sim-id?Ident=WD+1145%2B017">WD 1145+017</a> (also known as EPIC 201563164). They also detected similar but weaker signals – all with periods ranging between 4.5 and five hours. Using additional data from a range of Earth-based telescopes, they interpreted these dips as times when low-mass objects orbit in front of the white dwarf, blocking out some of its light. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/99174/original/image-20151021-15410-17049wm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/99174/original/image-20151021-15410-17049wm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=328&fit=crop&dpr=1 600w, https://images.theconversation.com/files/99174/original/image-20151021-15410-17049wm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=328&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/99174/original/image-20151021-15410-17049wm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=328&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/99174/original/image-20151021-15410-17049wm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=412&fit=crop&dpr=1 754w, https://images.theconversation.com/files/99174/original/image-20151021-15410-17049wm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=412&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/99174/original/image-20151021-15410-17049wm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=412&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Kepler and the area it is investigating.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/nasablueshift/4797426132">NASA Blueshift/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Although the behaviour of the dips with time is complex, the team thinks that at least six minor planetary objects with masses comparable to or smaller than <a href="https://theconversation.com/dawn-breaks-over-distant-ceres-and-perhaps-reveals-signs-of-habitability-38967">dwarf planet Ceres</a> orbit the WD 1145+017 white dwarf every 4.5 or 4.9 hours. The bodies appear to be rocky with <a href="http://hyperphysics.phy-astr.gsu.edu/hbase/dens.html">densities</a> greater than Pluto – at least two grammes per cubic centimetre. They also have comet-like dust tails produced when the incident radiation from the white dwarf heats up their surfaces, causing minerals such as <a href="http://www.minerals.net/mineral/orthoclase.aspx">orthoclase</a> and <a href="fayalite">fayalite</a> to form streaming metal vapours.</p>
<p>The astronomers also analysed the light from the star itself through <a href="https://theconversation.com/explainer-seeing-the-universe-through-spectroscopic-eyes-37759">spectroscopy</a> and could confirm that it is indeed polluted with elements including magnesium, aluminium, silicon, calcium, iron and nickel. These elements most likely ended up there in the past million years – very recently given the dwarf formed 175 million years ago.</p>
<h2>What does it mean for the Earth?</h2>
<p>When our own Sun dies it will initially expand to become <a href="http://www.universetoday.com/18847/life-of-the-sun/">a huge red-giant star</a> and engulf Mercury and Venus. Whether it will expand to reach Earth is still a <a href="http://www.scientificamerican.com/article/the-sun-will-eventually-engulf-earth-maybe/">matter of debate</a>. When its nuclear fuel is exhausted gravity will then cause the Sun to shrink down to about the size of the Earth itself but with a density so high that a teaspoon worth of this star would <a href="http://www.nasa.gov/topics/universe/features/whitedwarf_pulsar.html">have a mass</a> of nearly 15 tons. This evolutionary cycle could perturb the orbits of other planets in the solar system, increasing the chance that they would collide with each other and ultimately disintegrate and fall into the Sun, just like in the new study.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/99182/original/image-20151021-15421-1vurrti.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/99182/original/image-20151021-15421-1vurrti.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=453&fit=crop&dpr=1 600w, https://images.theconversation.com/files/99182/original/image-20151021-15421-1vurrti.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=453&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/99182/original/image-20151021-15421-1vurrti.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=453&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/99182/original/image-20151021-15421-1vurrti.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=570&fit=crop&dpr=1 754w, https://images.theconversation.com/files/99182/original/image-20151021-15421-1vurrti.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=570&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/99182/original/image-20151021-15421-1vurrti.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=570&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Internal structure of a Sun-like star and a red giant.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Giant_star#/media/File:Structure_of_Stars_%28artist%E2%80%99s_impression%29.jpg">ESO/wikipedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>The research could also help explain another major question in planetary science: whether the water on Earth was already present in the primordial material that formed our planet or whether it was planted here by collisions with other bodies. </p>
<p>Earlier this year another white dwarf, SDSS J1242, was found to have an atmosphere polluted with <a href="https://theconversation.com/polluted-dwarf-star-could-hold-the-key-to-the-origin-of-water-on-earth-41468">a large amount of oxygen</a>, which raised the possibility that a water-carrying asteroid might have planted it there. But it was not possible to directly detect the rocky debris that caused the pollution in this system. The new study provides compelling evidence for the connection between disintegrating rocky bodies and polluted white dwarf atmospheres.</p>
<p>Four billion years ago, the Earth and other rocky planets are thought to have been bombarded by comets and asteroids. While the asteroids in our solar system are today barren objects, the two studies indicate that they can indeed carry a number of heavy elements. Perhaps 4 billion years ago some of them contained water and perhaps even the complex organic molecules that provided the <a href="https://theconversation.com/explainer-what-philae-did-in-its-60-hours-on-comet-67p-34289">building blocks of life</a>. </p>
<p>The authors hope that future studies of WD 1145+017, and perhaps other systems, with transit spectroscopy might detect the presence of more complex molecules in the dust tails of the ill-fated debris.</p><img src="https://counter.theconversation.com/content/49520/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Carole Mundell receives funding from the Science and Technology Facilities Council, the Royal Society and the Wolfson Foundation. However, the views expressed here are her own and not those of the research council.</span></em></p>A study into a distant white dwarf could help us learn more about the future fate of the Earth – and it could be a violent one.Carole Mundell, Head of Astrophysics, University of BathLicensed as Creative Commons – attribution, no derivatives.