Supermassive black holes (SMBH) are difficult to explain. It is believed that these gigantic singularities are at the center of every great galaxy (our Milky Way has one), but their presence there is sometimes inexplicable. As far as we know, black holes form when huge stars collapse. However, this explanation does not fit with all the evidence.
The theory of star collapse provides a good explanation for most black holes. According to this theory, a star that is at least five times as massive as our sun will run out of fuel toward the end of its life. Since the external pressure of the nuclear fusion of a star supports it against the internal gravity of its own mass, something must yield when the fuel runs out.
The star goes through a hypernova explosion and then collapses. What remains is a black hole. Astrophysicists believe that SMBHs begin on this path and grow to their enormous size by essentially "feeding" on other things. They swell in size and sit in the center of their gravity like a spider that contracts in the middle of its web.
The problem with this explanation is that it takes a long time for it to happen.
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Many of these SMBHs are billions of times more massive than the sun?. They have such redshifts that they must have arisen in the first 800 million years after the Big Bang. For the star collapse model, however, this is not enough time to explain it. The question astrophysicists ask is how these black holes got so big in such a short time.
A team of researchers at Western University in Ontario, Canada, thinks they have found out. They have a new theory called "direct collapse" that explains these incredibly old SMBHs.
Her article is titled "The Mass Function of Supermassive Black Holes in the Scenario of Direct Collapse" and is published in The Astrophysical Journal Letters. The authors are Shantanu Basu and Arpan Das. Basu is a recognized expert in the early stages of star formation and the evolution of protoplanetary disks. He is also a professor of astronomy at Western University. This also comes from the Western Department of Physics and Astronomy.
The SMBH in this Subaru telescope image is 13.05 billion light-years from Earth. These old SMBHs have challenged our understanding of black hole formation. Picture credits: National Astronomical Observatory of Japan (NAOJ).
Their theory of direct collapse states that the ancient supermassive black holes have formed extremely rapidly in very short periods of time. Then they suddenly stopped growing. They developed a new mathematical model to explain these fast-forming, ancient black holes. They say that the Eddington boundary, which represents a balance between the outward radiant power of a star and the inward gravitational force, plays a role.
In these direct black holes, the Eddington limit regulates mass growth, and the researchers say that these old black holes may even slightly exceed this limit, what they call Super Eddington accretion. Due to the radiation generated by other stars and black holes, their production was discontinued.
"Supermassive black holes had only a short period of time in which they could grow quickly, and then at some point due to all the radiation in the universe created by other black holes and stars, their production stopped," explains Basu a press release. "This is the scenario of direct collapse."
"This is indirect evidence that black holes are caused by direct collapse rather than star remnants," Basu said.
This new theory provides an effective explanation for what has been a delicate issue in astronomy for some time. Basu believes that these new findings can be used with future observations to trace the genesis of the extremely massive black holes that exist in our universe at very early times.