Even dying stars can give birth to planets, suggest astronomers

New Delhi: In any galaxy, planets are usually no older than the stars around which they orbit. For example, the Sun was born 4.6 billion years ago, and the Earth came into the world shortly thereafter. But astronomers at KU Leuven have discovered that an entirely different scenario is also possible.

The study, published in the journal Astronomy and Astrophysics, describes the discovery. In the study, astronomers suggested that even if stars are near death, some of those types could possibly still form planets. If this is confirmed, then the theories of planet formation will need to be adjusted.

Planets like Earth, and all the other planets in our solar system, formed shortly after the Sun. Our Sun began to burn 4.6 billion years ago, and over the next million years, the matter around it coalesced into protoplanets. The birth of the planets in that protoplanetary disk, a giant pancake made of dust and gas, so to speak, with the Sun in the middle, explains why they all orbit in the same plane.

But such disks of dust and gas do not necessarily surround only newborn stars. They can also develop independently of star formation, for example around binary stars one of which is dying (binary stars are two stars orbiting each other, also known as binary systems). When the end reaches for a medium-sized star (like the Sun), it ejects the outer part of its atmosphere into space, after which it slowly dies as a so-called white dwarf.

However, in the case of binary stars, the gravitational pull of the other star causes the matter ejected by the dying star to form a flat, rotating disk. Furthermore, this disk strongly resembled the protoplanetary disk that astronomers see around young stars elsewhere in the Milky Way.

This was an already known fact. What is new, however, is that the disks around so-called evolved binary stars do not unusually show signs that could indicate planet formation, as observed by an international team of astronomers led by KU Leuven researchers. has been searched.

What’s more, their observations showed that this is the case for one in ten of these binary stars. “In ten percent of the evolved binary stars in the disks we studied, we see a large cavity (a void/opening, ed.) in the disk,” says KU Leuven astronomer Jacques Kluska, first author of the study. “It’s a sign that there is something floating there that has collected all the matter in the area of ​​the cavity.”

Cleaning up the matter can be the work of a planet. That planet may not have formed at the very beginning of the life of binary stars, but at the very end. In addition, astronomers found even stronger indications for the presence of such planets.

“In evolved binary stars with a large cavity in the disk, we observed that heavy elements such as iron were very rare on the surface of the dying star,” Kluska said. “This observation leads one to suspect that dust particles rich in these elements were trapped by a planet.” By the way, the Leuven astronomer did not rule out the possibility that in this way many planets could form around these binary stars.

The discovery was made while astronomers were preparing a catalog of the binary stars that evolved in our Milky Way. He did this based on existing, publicly available comments. Kluska and his colleagues counted 85 such binary star pairs. Of the ten pairs, the researchers found a disc that contained a large cavity to capture infrared images.

If new observations confirm the existence of planets around evolved binary stars, and if it turns out that planets formed only after a star had reached the end of its life, theories of planet formation would need to be adjusted. Will be According to Professor Hans Van Winkel, Head of the KU Leuven Institute of Astronomy, “the confirmation or refutation of this extraordinary method of planet formation would be an unprecedented test for current theories”. (ANI)

First Published:February 1, 2022, 5:41 pm


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