Planetary debris, torn apart by the tidal forces of dying stars, then revolves around white dwarfs in a cloud that is a reservoir of material that gradually falls on the star, thus polluting its atmosphere. In general, these very dense objects on the contrary should cause the heaviest elements to sink very quickly into their cores, leaving the lightest elements on the surface, helium and hydrogen, the two main components of the atmosphere of white dwarfs. Analysis of the emission spectra of the so-called “polluted” atmospheres revealed the formation of clouds that formed around the studied stars, indicating that this formation is in fact the formation of destroyed planets. “In previous articles, scientists believed that they had discovered pieces of the thinner crust of rocky planets, but this new study shows that it is not possible to unambiguously identify this component and that the discovered elements are also compatible with pieces of the mantle, that is, from deeper, more abundant and more common layers of the planets “, identifies Philippe Delorme, an astronomer at the University of Grenoble.
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As part of the study published intemper natureIn November, 23 polluted white dwarfs were observed, all within 200 parsecs of the Sun (about 652 light years). The result presented by the scientists essentially determines that the atmosphere of these dwarfs presents a much greater variety of materials than we know in the Solar System. Even new rock names had to be developed, such as ‘quartz orthoproxenites’, ‘pyricase clinoproxenites’, etc.
These polluted clouds, which moreover represent a mixture of the composition of all possible planets destroyed around the corresponding star, will therefore be a new indication of the presence of unusual substances.In a way, that’s not surprising., Comments by Philip Delorme.“Our solar system has only eight planets, and we have already discovered more than 4,500, including ‘super-terrestrial planets’, which are rocky planets several times larger than Earth, common in the universe, but absent from the solar system.”, continues the astronomer. The planets of the solar system do not reveal the full diversity of the galaxy,“So it’s statistically normal for other planets to represent more diversity.”.
Illustration of a white dwarf. Credit: shutterstock.
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A new way to observe exoplanets
If the study provides a result that is not surprising in the end, then Philippe Delorme, on the other hand, considers that the main interest of this work lies in the scientific approach. Scientists can anticipate a variety of hitherto unknown materials,“But that’s his style of showing it, and it’s new here.”. It is a result that confirms the theory of great diversity, since in science,“When two completely different methods show the same result, it is somewhat reassuring.”Researcher continues.
This method of observation by analyzing the spectra of debris is also a new way to understand planetary systems orbiting white dwarfs. In general, planets are actually detected singly and indirectly, for example by observing the variation in the luminosity of stars orbiting them. In the case of observed pollution of white dwarfs, on the other hand, they are just a mixture of ancient planets, and therefore the exact composition of each individual planet cannot be determined.
In addition to observing the heavy elements corresponding to the formation of planets in the atmosphere of white dwarfs,“You need a recent contribution to be able to discover it before you fall into the star.”; Philippe Delorme adds. So the pollution of the white dwarfs changes when they swallow the cloud of debris orbiting them.“Maybe in a few hundred years, these white dwarfs will no longer be polluted.”Imagine a researcher looking at the evolution of these solar-type stars.“And then one day, history will repeat itself with the debris of Earth and other planets in the solar system.”.
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