British scientists have built a computer model of planet formation in red dwarf systems and have shown that, contrary to popular belief, large and hot planets can form very quickly around such stars. The research results are published in the journal Astronomy and Astrophysics.
Red dwarfs are small stars no more than half the size of the Sun - the most common type of star in our Galaxy. Despite the small mass of such stars, astronomers find giant planets around them, which are 10 times larger than Jupiter - the largest planet in the solar system.
The formation mechanism of these giant planets remains an unsolved mystery, because the giant planets of the solar system - Jupiter and Saturn - were formed as a result of gradual growth due to the accumulation of dust particles. And around red dwarfs, according to most scientists, there is not enough material for the slow formation of large planets.
A new study by scientists from the University of Central Lancashire (UK) shows that giant planets can form around small stars, but the process of their formation is very fast.
To simulate the evolution of protoplanetary disks around red dwarf stars, the authors used the distributed capabilities of the Advanced Computing (DiRAC) supercomputer facility.
Protoplanetary disks are rotating structures of dense gas and dust that surround all newborn stars. The researchers found that when these disks are large enough, they can disintegrate into blobs of gas from which giant planets are formed. This process takes place over several thousand years, which is extremely fast in the astrophysical sense.
"The fact that planets can form in such a short time around tiny stars is incredibly exciting," study leader Anthony Mercer said in a university press release. "Our work shows that planetary formation is a common process. Other worlds can form even around small stars, and this happens in different ways. Therefore, the planets can be much more diverse than we previously thought."
The model also implies that giant planets forming around red dwarfs must be very hot - the temperature in their cores reaches thousands of degrees. These hot planets can be easily observed while they are young. But they quickly fade, since they have no internal source of energy, and the window of opportunity for direct observation of them is very small.
However, it can be observed indirectly, fixing their influence on the parent star. This is how many such planets around small stars were discovered.
"This was the first time that we were able to use computer simulations to not only see the formation of planets, but also to determine their initial properties in great detail. It was amazing to find that these planets can form so quickly and be so hot," says the second author articles by Dimitris Stamatellos.
Only future observations will be able to verify how correct the new theoretical constructions are.
