"The puzzle has been how these 'seed' black holes grew into the monsters that we now see within the time available, a few billion years at best," says Priyamvada Natarajan, who proposes that early quasars took in a "super boost," feasting from large reservoirs of gas that were part of early star clusters. (Credit: Lollito Larkham/Flickr)

‘Monster’ quasars got that way by gorging on gas

Feasting on the dense, cold, gas flows of the early cosmos may have given the universe’s oldest quasars the means to become monsters within only a few billion years.

For years, scientists have tried to explain the intense luminosity of quasars in the early universe. Quasars’ light is powered by swirling gas that is pulled in from the gravity of black holes. Located in the deepest precincts of space, the energy emitted by this infalling gas reveals the presence of black holes.

Yet the earliest quasars—those dating from when the universe was barely a billion years old (today the universe is 13.8 billion years old)—have proved baffling.

Their brightness suggests they harbor black holes with a million times more mass than the Sun and scientists have been at a loss to understand how these behemoths assembled so rapidly, by cosmic standards.

“The first black holes are believed to be remnants left behind after the first stars burned out completely,” says Priyamvada Natarajan, professor of astronomy and physics at Yale University. “The puzzle has been how these ‘seed’ black holes grew into the monsters that we now see within the time available, a few billion years at best.”

Celestial smorgasbord

Natarajan and fellow researcher Tal Alexander of the Weizmann Institute have come up with a possible answer: early quasars took in a “super boost,” feasting from large reservoirs of gas that were part of early star clusters.

The robust, volatile nature of the early universe made such conditions quite likely. New black holes were swept up into a celestial smorgasbord of gas in the star clusters that harbor them. This motion, in turn, circumvented normal restrictions that would prevent black holes from gorging on gas at a much-accelerated rate.

“There is a new way to super boost the growth of early black holes and make them very massive within a very short time in the early universe,” Natarajan says.

“We realized that the setting where this kind of unbridled growth of initial seeds can occur was found to be commonplace in numerical simulations of the early universe.”

The National Science Foundation, with a grant from the Theoretical and Computational Astrophysics Network, supported the research, which is published in the journal Science.

Source: Yale University

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