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When the majority of stars reach the end of their lives, they make their own funeral pyre, throwing away the essence of their gas in a glorious depiction of their immense power and leaving behind a dense and ashy nucleus called white dwarf. But what happens to the planets orbiting such a star? It's hard to answer this question, but scientists now claim that they have detected the remnant of a white dwarf world, an unprecedented discovery that could offer a fascinating glimpse into the disappearance of planetary systems across the universe.
In an article published Friday in Science, A team led by Christopher Manser of the University of Warwick in England reports unprecedented observations of a white dwarf slightly larger than Earth but containing almost the mass of the sun. Called SDSS J1228 + 1040, the star is located about 410 light-years from the planet. It is more specifically called "polluted" white dwarf because of the heavy elements that astronomers can detect if it rains on its surface. It is believed that this material comes from a gas disk that surrounds the object. And in this disc, the authors of the newspaper found ghostly remains of a planet.
"It's like the iron core left by a larger body that has been torn apart," says Manser. "The crust and mantle have been removed from this body. We end up with this iron core in orbit around which has a great internal strength keeping it, not just gravity. "
The white dwarf-wide debris disk, three million kilometers wide, was first discovered more than 15 years ago, making the star one of the least d & # 39; 39, a dozen polluted white dwarves known to be surrounded by discs. When a star of less than eight solar masses exhausts its fuel with hydrogen, it expels the outer layers, thus engulfing the nearest planets. It is thought that some of these worlds could then be torn apart, after which their shredded remains are collected in such a disc. And although more than 4,000 exoplanets have been discovered to date, scientists have only seen one single proof of this process: the remains of a planet in a disk around the white dwarf WD 1145 + 017, which was the subject of a comprehensive study in 2015.
While these planetary remains gravitate around WD 1145 + 017 in 4.5 hours, the heavy metal ring encircling SDSS J1228 + 1040 revolutionizes in less than half that time. The authors of the new study detected the star's dense companion using the 10.4 meter Gran Telescopio Canarias (GTC) on the Canary Islands during two separate observation periods in April 2017 and April and May 2018, respectively. . By dividing the light emitted by the white dwarf into its constituent wavelengths – a bit like a prism – by dividing the white light into a rainbow – the team detected the disc and recorded corresponding color changes. to its orbital movement.
Generally, this method is used to observe systems such as SDSS J1228 over long periods of years, but by studying this white dwarf for several hours, the team discerned a mass of material in the disk that had a lag that was entirely his. own. The force of the group suggests that its source was a solid object of some 600 kilometers – a presumed planetary nucleus, with a density of between 7.7 and 39 grams per cubic meter, which is comparable to the pure iron contained in the nucleus of the Earth. "The density of the piece of rock is consistent with what we think the kernels of the planets [are]"Says Luca Fossati, of the Austrian Academy of Sciences, who did not participate in the newspaper. "It's a big problem. This basically confirms the idea that we have these discs of dust and debris that revolve around some white dwarfs are [the remains of] ancient planets. "
The discovery of a small planet orbiting a white dwarf star, how some flightless birds may have lost their flight and the subsequent meiosis in corn – and so much more in our last number. https://t.co/0m5UC7pFyw pic.twitter.com/LIaB8vTbzv
– Science magazine (@sciencemagazine) April 4, 2019
The shift also indicated that the bunch was in orbit only half a million kilometers from the star – an extremely close distance at which larger, less dense objects would be stretched and torn by the intense gravitational field of the white dwarf . This disordered disassembly, described at the extreme of "spaghettification" by astrophysicists, is the typical fate of everything that falls into a black hole. But around the white dwarf, where gravity is not so extreme, a small dense and dense core of heavy metals could survive. "If you have a small enough object, it's easier to resist spaghettification," says Andrew Vanderburg of the Harvard-Smithsonian Astrophysical Center, who also did not participate in the journal. "What [the researchers] Here we find that the planet rotates so close to its star that it must be maintained by material force. "
With a specific orbital period of 123 minutes, this core would set a new record for the fastest planetary object orbiting a star; The previous record was exoplanet KOI 1843.03, which ends an orbit in 4.25 hours. The bizarre system also offers a unique scientific opportunity to scrutinize the exposed core of an exoplanet, although astronomers currently have no telescope large enough to directly see the nucleus.
Perhaps, however, similar objects are waiting to be discovered around other white dwarves. Whether they study them alone or in multitudes, such heavy-metal worlds can offer bleak predictions about the future of our own solar system, when our sun's fuel runs out of energy. here five billion years. "It's really exciting, because it's a bit of the missing piece, if you will, [of white dwarf planetary systems]Says Sarah Casewell from the University of Leicester in England, who did not participate in the research. "We know that great things can survive and that little things are destroyed. It's a pretty considerable rock object that has survived.
This article is reproduced with the permission of Scientific American. You can see the original story here.
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