First black holes may have incubated in gigantic starlike cocoons
Washington: In a new study, scientists at the University of Colorado at Boulder have determined that the first large black holes in the universe likely formed and grew deep inside gigantic, starlike cocoons that smothered their powerful x-ray radiation and prevented surrounding gases from being blown away.
The predecessors to black hole formation, objects called supermassive stars, probably started forming within the first few hundred million years after the Big Bang some 14 billion years ago.
In the new study, Mitchell Begelman, a professor and the chair of CU-Boulder’s astrophysical and planetary sciences department, calculated how supermassive stars might have formed, as well as the masses of their cores.
These calculations allowed him to estimate their subsequent size and evolution, including how they ultimately left behind “seed” black holes.
Begelman said that the hydrogen-burning supermassive stars would had to have been stabilized by their own rotation or some other form of energy like magnetic fields or turbulence in order to facilitate the speedy growth of black holes at their centers.
“What’s new here is we think we have found a new mechanism to form these giant supermassive stars, which gives us a new way of understanding how big black holes may have formed relatively fast,” said Begelman.
“The main requirement for the formation of supermassive stars is the accumulation of matter at a rate of about one solar mass per year,” he said.
Because of the tremendous amount of matter consumed by supermassive stars, subsequent seed black holes that formed in their centers may have started out much bigger than ordinary black holes - which are the mass of only a few Earth suns - and subsequently grew much faster.
After the seed black holes formed, the process entered its second stage, which Begelman has dubbed the “quasistar” stage.