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Recent fluctuations in the luminosity of a very young star would be caused by the matter released by repeated collisions between rocky planetary bodies. Fragments of these bodies would fall on this star, a phenomenon predicted but never observed for a young sun of a few million years.
Since Descartes, Kant and Laplace, we have made gigantic progress in the theory of the formation of the Sun. System. The first big leap forward came in the second half of the twentieth century with analytical and numerical models of planet formation derived from the theory of accretion initially developed by researchers like Viktor Safronov and George Wetherill. The second leap forward, which also accompanies the progression of numerical simulations, comes mainly from the progress of observational astronomy for a quarter of a century and which shows us the accretion discs around young people. stars in stellar nurseries, as well as exoplanets. 19659003] We still do not understand everything in the cosmogony of planetary systems and there are still some shadow areas concerning the birth of giant planets in the solar system. This is why astronomers and astrophysicists who deal with these issues are relentlessly sweeping some cosmic nurseries for additional information to test. One of the most interesting is that located on the borders of the Taurus and Bouvier constellations (a region called Taurus-Auriga), which includes the Taurus Molecular Cloud (TMC-1) 1), a molecular cloud located about 450 years ago -light. of the Sun and which would be the most important region of star formation closest to the Solar System.
Also in this region of the celestial vault, scientists have observed since 1937 the intriguing (not as much as those of the Tabby star) solar-type star-type RW brightness variations Aur A, which constitutes a binary system with another similar star RW Aur B. These stars have a few million years and RW Aur A is still surrounded by his protoplanetary disk rich in gas and dust in which the formation of gas giants is probably in progress. We know that this type of disc dissipates after about 5 to 10 million years, which means that in the case of the Solar System, Saturn and Jupiter have necessarily formed before dissipating an equivalent disk. # 39; having. – even existed for a similar duration.
Significant declines in the brilliance of RW Aur A usually occur after a few decades and last about a month. However, in 2011, the luminous flux of the star has further declined, but for about half a year. The decrease in brightness was then repeated in mid-2014 and it is only in November 2016 that the star becomes "normal" again. What could be due to this phenomenon?
Astrophysicists are on a track thanks to observations in the X-ray field of the Chandra satellite and they have advanced a hypothesis that they explained in an available publication on arXiv. Indeed, RW Aur A saw its brightness drop again in January 2017 and this time Chandra allowed to observe for a total of 14 hours. The X emissions came from both the star itself and the disk as the RW Aur A radiation in that same band of the electromagnetic spectrum scattered. Two results have been deduced, including a particularly surprising one. The first is that the star is warmer than we thought and the second is that some parts of the disc and especially the atmosphere of the star are much richer in iron than expected due to the dependence between the star temperature and the composition of its protoplanetary disk by a factor of about 10. Typically hot and active stars have less iron than others, while RW Aur A seems have more in his crown for some time compared to previous observations.
The most attractive idea for researchers is that it would be the result of recent collisions between two planetary celestial bodies large enough for them to differentiate and form the equivalent of the rich kernel. iron and nickel in the center. of the earth. We know that this type of phenomenon can occur because in the solar system itself, siderite-type meteorites made up in the vast majority of an alloy of iron and nickel are supposed to be the remains of similar collisions.
such collisions would then release the iron and nickel trapped in large planetesimals, probably several hundred kilometers in radius, or even in a planetary embryo of terrestrial type. This would explain the sudden iron enrichment of the protoplanetary disk and the star's crown. The gases and the released dust also blocking the star's light would be due to recent luminosity decays with repetition in the visible spectrum.
Many of these collisions have occurred in recent years, and it is likely that they are in fact repeated collisions between debris left behind by larger collisions. The iron enrichment of the crown RW Aur A would be due to the arrival on the star of some of these debris
If that is the case, then it is a great first, watching the remains of planets falling on a young star. This type of scenario was previously limited to computer numerical simulations of planetary system formation.
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