As astronomers and cosmologists attempt to piece together the formation of the universe, some of the pieces are truly immense. For example, supermassive black holes, which are believed to be associated with nearly every large galaxy, are billions of times larger than the sun. A new model connects the supermassive black holes to equally massive stars formed not long after the Big Bang.

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, says a new study led by the University of Colorado at Boulder.

The formation process involved two stages, said Mitchell Begelman, a professor and the chair of CU-Boulder’s astrophysical and planetary sciences department. 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. A supermassive star eventually would have grown to a huge size — as much as tens of millions of times the mass of our sun — and would have been short-lived, with its core collapsing in just in few million years, he said.

The main requirement for the formation of supermassive stars is the accumulation of matter at a rate of about one solar mass per year, said Begelman. 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. In this phase, black holes grew rapidly by swallowing matter from the bloated envelope of gas surrounding them, which eventually inflated to a size as large as Earth’s solar system and cooled at the same time, he said.

Once quasistars cooled past a certain point, radiation began escaping at such a high rate that it caused the gas envelope to disperse and left behind black holes up to 10,000 times or more the mass of Earth’s sun, Begelman said. With such a big head start over ordinary black holes, they could have grown into supermassive black holes millions or billions of times the mass of the sun either by gobbling up gas from surrounding galaxies or merging with other black holes in extremely violent galactic collisions.

[Source: EurekAlert]

Cosmological theory has held that supermassive black holes were formed by merging numerous much smaller black holes. The new model provides an alternative explanation, based on matching the known behavior of star collapse in the formation of black holes and the supermassive size of early stars. As with all cosmological models, the proof is in the discovered evidence. In this case, scientists may be able to use NASA’s James Webb Space Telescope, slated for launch in 2013, to look back in time and hunt for the cocoon-like supermassive stars near the edges of the early universe. If they exist, they would shine brightly in the near infrared portion of the electromagnetic spectrum, and would provide serious confirmation for the model.