Many secrets drift in the cosmic ocean, ohthe existence of which we do not even guess. One of these was discovered five years ago when astronomers discovered a lone star 570 light-years from Earth, whose brightness dimmed irregularly every 4.5-5 hours. After close examination, it turned out that this is a white dwarf "WD 1145 + 017", which absorbs the planets of its system. The discovery marked the beginning necroplanetology - perhaps the most unusual field of astronomy,which studies the fate of already dead planets. Like necromancers from fantasy works, astronomers resurrect dead planets to find out about their past, trying to simulate what these distant worlds were, what they consisted of and which influenced other objects of their star system. Moreover, the study of such planets can tell a lot about the death of stellar systems themselves.
What is necroplanetology and how did it come about?
WD 1145 + 017 - a star in the constellation Virgo. The distance from Earth is about 570 light years. This means that what we now see through telescopes happened to a star 570 years ago. Journey into the past, not otherwise!
In 2015, astronomers noticed that WD 1145 + 017 was fading at an irregular rate, and after close examination they realized that a star devours planets in its solar system through a process called tidal flare - when a star approaches the event horizonsupermassive black hole and it tears apart by tidal forces, through "spaghettification". Read more about what it is and why, once in a black hole, you also turn into spaghetti, read our material. It is noteworthy that it took as long as five years for the study to be accepted for review in The Astrophysical Journal. All this time, the work was in the public domain on the preprint server in arXiv.
White dwarf - in simple words, then this is a star devoid of sources of thermonuclear energy. In fact, it just cools down and dims, like a recently disconnected electric stove burner
Right before becoming a supernova orturn into a black dwarf, dying stars become white dwarfs. Our Sun is also waiting for such a fate, but fortunately, not earlier than in six billion years. White dwarfs are devoid of sources of thermonuclear energy and glow weakly, gradually cooling and blushing. The atmospheres of such stars usually contain lighter elements such as helium and hydrogen. It was thanks to the study of the atmosphere of WD 1145 + 017 that astronomers realized that the white dwarf discovered by them behaves somewhat unusual: the brightness of the star decreased by different values every 4.5-5 hours, and traces of elements that are usually found in rocky cores were discovered in its atmosphere planets - iron, oxygen and magnesium.
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To find out how the planets met theirdeath, the researchers created a series of computer simulations that showed how 36 different types of planets would react to absorption by their native star. The results showed that most often rocky planets withstood the main stage of destruction, but decayed within a short period of time. It is important to understand that all the described processes lasted thousands of years. The reason that no small objects were found around the white dwarf WD 1145 + 017 is that all the debris of the planets is absorbed by the monstrous force of gravity. The remnants of the planets lose their mass and shape - for this reason, the brightness of the star dims.
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So necroplanetology kills right awaytwo birds with one stone - with its help, scientists can simultaneously study the death of white dwarfs and planets, gradually restoring the chronology of events and how the evolution of stellar systems occurs. So, over the past year alone, more than 20 dying star systems were discovered, in each of which the remains of dead planets contain valuable information. This became possible, as astronomers explained the similar behavior of other stars, which in the past caused heated debate in the academic environment. It turned out that the stars were simply dead, and the surrounding cosmic bodies formed by gravity created the effect of darkening the glow.
So, studying the remains of the lost planetsresearchers learn about their rate of destruction. In the future, the restoration of their former appearance will allow modeling the entire star systems in which these distant worlds were born, as well as a glimpse into the past galaxies. Ultimately, a series of future discoveries will help to better understand the structure of our universe. By the way, despite its name, the field of necroplanetology is thriving today and this cannot but rejoice.