Of all the prevailing ideas for how black holes emerge, none could account for the existence of an impossibly large type of black hole detected in 2019 鈥� but now we may know how it could have formed.
In May 2019, researchers at the Laser Interferometer Gravitational-Wave Observatory (LIGO) in the US and its Italian counterpart Virgo measured ripples in space-time called gravitational waves and determined that their signal was the result of two black holes merging.
Stellar-mass black holes like these arise when a star becomes too large to support its own weight and explodes in a supernova, its inner layers collapsing in on themselves.
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However, this process was thought to only produce black holes up to about 65 times the mass of the sun because the winds that blow away the outer layers of the star during the supernova remove so much mass that it limits the size of the resulting black hole.
The larger of the two black holes detected by LIGO and Virgo had a mass 85 times that of the sun, so seems to be larger than previously thought possible.
at the Armagh Observatory & Planetarium in Northern Ireland and his colleagues performed simulations of stars that may have formed billions of years ago and found that they could be the progenitors of larger black holes.
These stars would have contained higher proportions of heavy elements than those formed more recently, which means they could have remained relatively compact throughout their life cycles. So, when they went supernova, they wouldn鈥檛 have blown away as much material in the explosion.
鈥淲e can keep most of [the star鈥檚 mass] intact and actually form these 85-solar-mass black holes, which we thought were impossible,鈥� said Vink. He presented this work at a meeting of the American Astronomical Society on 7 June.
This could help us understand how聽supermassive black holes 鈥� which can be billions of times as massive as the sun 鈥� formed in the early universe, a long-standing mystery in astrophysics. 鈥淚t doesn鈥檛 solve the problem鈥� but it gives us more insight into the physics,鈥� said Vink. Similar processes could govern the formation of extra-large stellar-mass black holes and their supermassive cousins.
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