The biggest black holes in the universe are also the most perplexing. Scientists have long been confused about just how the earliest, most massive black holes formed, but new evidence now suggests they could have originated inside giant cocoon-like stars.
This idea is at odds with the prevailing thinking that large black holes are created by the clumping together of smaller black holes.
Not so, says University of Colorado at Boulder astrophysicist Mitchell Begelman. Rather, these behemoth black holes likely formed in the middle of even larger supermassive stars that could have held tens of millions of times the mass of our sun, according to Begelman.
"Until recently, the thinking by many has been that supermassive black holes got their start from the merging of numerous, small black holes in the universe," Begelman said. "This new model of black hole development indicates a possible alternate route to their formation."
Begelman studied how these gigantic stars could have formed, and how massive their cores might have been, to understand how they might have given rise to huge black holes. The results of his investigation will be published in an upcoming issue of the Monthly Notices of the Royal Astronomical Society in London.
The monster stars probably started forming within the first few hundred million years after the Big Bang, which is thought to have created the universe around 14 billion years ago, Begelman found. When the cores of these giant stars had burned all their hydrogen, they would have collapsed, forming dense black holes. Meanwhile the outside gas layers of the stars remained as a shroud. Eventually, though, the black holes would have swallowed all the remaining stellar matter within their reach, ballooning rapidly to staggering weights, the study suggests.
This scenario could be more likely than the clumping process as the origin of supermassive black holes, Begelman said, though it's also possible that both methods have occurred.
"The problem that most people see in the clumping mechanism is whether you get these small black holes to merge frequently enough," Begelman told SPACE.com. "I'm working on trying to compare the rates of these two processes."
Over time, the resulting black boles might have merged with other giant black holes to form even larger leviathans.
"Big black holes formed via these supermassive stars could have had a huge impact on the evolution of the universe, including galaxy formation," Begelman said.
Astronomers think most galaxies, including the Milky Way in which the Earth's solar system resides, have supermassive black holes at their centers. These black holes are probably responsible for a cosmic phenomenon called quasars, which are thought to occur when mass pours onto huge black holes, and some material is flung away in bright jets of high-energy radiation that can be seen across the universe.