Heavy metals, iron and nickel, allowed a fragment of the dead planet to survive the destruction of the planetary system, said astronomers at Warwick University (UK) in the journal Science. Scientists have found a small body in the disk of debris surrounding the dead star at a distance of 410 light-years from the Earth, and the orbital ring of comet-like gas tails, escaping from this piece of ancient exoplanet. And this is a new look at the future of the solar system in 6 billion years.
This is the first time we have used spectroscopy to detect a solid body in orbit around a white dwarf by capturing the subtle changes in the emitted light that have made it possible to identify the gas that emits the planetesimal.
The iron- and nickel-rich fragment survived a system-wide cataclysm following the death of its main star, SDSS J122859.93 + 104032.9. It has been established that it was once part of a larger exoplanet, and its survival becomes even more surprising as it orbits closer to its star than was generally thought possible, bypassing it once every two Earth hours.
Using the Gran Telescopio Canarias telescope on the island of Palma (Canary Islands), scientists have studied the debris disk around a white dwarf formed by the destruction of stony bodies consisting of elements such as iron, magnesium, silicon and oxygen – four key building blocks of the Earth. Inside this disk, they found a ring of gas flowing out of the solid like a comet’s tail. This gas can be generated both by the object itself and by the dust evaporating from it when the planetesimal collides with small fragments inside the disk. Astronomers have calculated that the size of the body should be not less than a kilometer, but can reach several hundred kilometers, which is comparable to the largest asteroids in the solar system.
White dwarfs are the remains of sun-like stars that have exhausted all their fuel and dropped the outer layers, leaving behind a slowly cooling dense core. Initially, the star SDSS J122859.93 + 104032.9 had about two solar masses, but now the starry residue is only 70% of the Sun’s mass. It is also very small, about the size of the Earth, making it and all white dwarfs generally extremely dense. Their gravity is so strong – about 100,000 times greater than the Earth’s – that a typical asteroid will be torn if it passes too close to a dead star.
The planetesimal we found is deep in the gravitational well of a white dwarf, much closer than we expected to find anything alive. This is only possible if it was initially very dense and very likely to have an inner strength, so we assume that it consists mainly of iron and nickel. If this is the case, the original body had a diameter of at least hundreds of kilometers, because only at this point do planets begin to differentiate themselves as oil on water, and heavier elements sink into the metal core.
-Professor Boris Gaencik, co-author of the study
The future of our solar system
The discovery hints to astronomers that the Sun and the entire solar system are expecting in 6 billion years.
As they age, sun-like stars turn into red giants that cleanse a large proportion of the interior of their planet system. In particular, our star will expand to Earth’s orbit and destroy it, Mercury and Venus. Mars and the outer planets will survive and continue their movement around the red giant, which, having dropped the outer layers, will become a white dwarf.
-the leading author of the study, Dr. Christopher Manser
On ruins of planetary systems gravitational interactions are not excluded, and it means that the big planets can easily push smaller bodies on spiral orbits in a direction to a star nucleus where they will be torn off by powerful gravitation. The study of fragments of exoplanets that can reach the center of the system sheds light on the surviving bodies that are far from the star and have not yet been observed.
Our discovery is only the second solid planetesimal found in a low orbit around a white dwarf. The transit geometry of such bodies must be very accurate, and a few hours of observations usually do not lead to anything. The spectroscopic method we have developed allows us to detect close objects without the need for precise alignment. We plan to begin studying several very similar to SDSS J122859.93 + 104032.9 systems with fragmentation disks and are confident that we will find additional planetesimals rotating around white dwarfs, which will allow us to learn more about their general properties and the fate of the planets that survived the death of their system.
A fragment of the planet that survived the death of a star has been discovered
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