A dead star has been observed destroying and absorbing its own planets
When a star dies, what happens to its planets? If this star is one white dwarf 86 light-years away from us, its planets have not really had a good day – they are now fluttering and swallowing their own star, as if it were a cosmic analogue of the ancient Greek Cronus swallowing its own children.
Such a thing is not so foreign to white dwarfs, but this particular star, named G238-44, is too greedy: astronomers first observed that such a star (white dwarf) simultaneously senses the matter of both the inner and outer part of its planetary system.
In the atmosphere of G238-44, astronomers have found traces of elements that indicate that this dead star has recently absorbed metal and rock material, similar to asteroids in the inner part of the solar system, as well as icy material in the outer body of the sun In part, it is found in the Kuiper belt.
“We have never seen both such objects in the white dwarf freeze at the same time. “Hopefully, studying such white dwarfs will give us a better idea of the still intact planetary systems,” said Ted Johnson, a physicist and astronomer at the University of California, Los Angeles.
The white dwarf is an object that stays in the sun for a maximum of eight times after the death of a massive star. Once such a star depletes the material needed for synthesis, it ages and becomes a red giant, then the outer layers of matter collapse, and the stellar nucleus collapses under gravity to form a dense object that glows with residual heat. This is a white dwarf.
This process must be quite painful for the planets orbiting the star – a few billion years later, when the sun turns into a red giant, it may even reach the orbit of Mars; However, recently astronomers have discovered evidence that some part of the planetary system may survive this process.
Exoplanets have been found around white dwarfs. There is necroplanetology – a field that studies the remains of white dwarf exoplanets based on traces of “polluting” heavy elements in the white dwarf atmosphere.
Because white dwarfs are very dense objects (imagine that the sun’s mass is concentrated in the Earth’s size), heavy elements must sink into it fairly quickly, which means that in order to detect traces of heavy element pollution in its atmosphere, they need to be new there. .
This is a very exciting story, because it means that we have the opportunity to study the entrails of exoplanets indirectly. We know what the Earth is made of, we know to some extent the composition of the other planets in the solar system, but other, it is impossible to study exoplanets moving in the same way as distant stars as we study the Earth or even other planets in the solar system.
Most of the planetary systems discovered by this time are very different from the solar system; The study of exoplanets destroyed by white dwarfs will help scientists determine whether the exoplanets’ entrails are different from the locals. Let’s go back here again to the white dwarf G238-44.
Johnson and his colleagues found that this white dwarf’s atmosphere-like pollution has not been recorded anywhere else so far. It contained ten elements heavier than helium: carbon, nitrogen, oxygen, magnesium, aluminum, silicon, phosphorus, sulfur, calcium, and iron.
Iron and nitrogen were especially abundant; According to the researchers, iron indicates the presence of a body with a differentiated iron nucleus, while nitrogen indicates the presence of icy bodies.
“The recorded data were best explained by a mixture of about two or three materials similar to Mercury and Comet. Iron and nitrogen ice indicate a very different environment of planetary formation. “We do not know of any such objects in the solar system,” Johnson said.
The results also indicate that the ingredients needed to create a life-friendly planet should not be uncommon in Milky Way. Earth is a rocky planet and is thought to have been filled with elements necessary for life, such as water and asteroids. Fixation of nitrogen-rich material may mean that frozen reservoirs of these elements may be quite common.
“The familiar form of life requires a rocky planet covered with various volatile elements, such as carbon, nitrogen, and oxygen. “These elements we’ve seen in abundance in white dwarfs seem to come from a rocky parent body and an acorn-rich parent body – this is the first such example we’ve found after studying hundreds of white dwarfs,” said Benjamin Benjamin, a physicist and astronomer at the University of California, Los Angeles.
About 5 billion years later, when our sun turns into a white dwarf, if any extraterrestrial civilization observes it, it will probably see something like this. In the process of expansion, the inner objects of the solar system may evaporate, but the asteroid belt between Mars and Jupiter may have survived, which could have been dispersed by a destabilized Jupiter and rained down on a dead star.
The group presented the study at the 240th meeting of the American Astronomical Society.
Prepared according to newsroom.ucla.edu and ScienceAlert.