Advanced model explains the existence of early massive black holes

Nov 8, 2013 07:55 GMT  ·  By
The various stages encountered during the collapse of a fragmenting supermassive star, according to the new model developed at Caltech
   The various stages encountered during the collapse of a fragmenting supermassive star, according to the new model developed at Caltech

Scientists with the California Institute of Technology (Caltech) say that discoveries made in a new study could one day help shed some light on how supermassive black holes (SMBH) – the largest such structures in the Universe – developed when the Cosmos was just a fraction of its current age. 

The research will be used to test a new model seeking to explain how very large black holes appeared and developed only a few hundred million years after the Big Bang. Under current theories explaining how these objects grow, their presence so far back in time is impossible.

According to existing data, black holes grow by accumulating material from nearby cosmic objects, such as gas clouds, nebulae, stars, neutron stars, and so on. Another way to boost their volume is by merging with other black holes. However, none of these processes was available very early on.

If mergers and matter accumulation were the only ways for a black hole to grow, the Caltech team explains, then supermassive black holes should have not been able to form at a time when other black holes were just appearing. Their new study may offer some hints on how to explain this issue.

Some hypotheses suggest that structures called seed black holes existed in the early Universe, produced by the supernova blasts of the earliest massive stars. Astrophysicists say that these seeds may have been the core around which the first supermassive black holes formed.

“But in these previous models, there was simply not enough time for any black hole to reach a supermassive scale so soon after the birth of the universe,” explains the lead author of the study, Caltech Einstein Postdoctoral Fellow in Astrophysics Christian Reisswig.

“The growth of black holes to supermassive scales in the young universe seems only possible if the ‘seed’ mass of the collapsing object was already sufficiently large,” the expert adds. He and his team found in the new study that supermassive stars may hold the answer to this mystery.

Such stars are believed to have existed only for a very short period of time in the history of the early Universe. Astronomers say that these objects remained in hydrostatic equilibrium – where photon radiation balances the gravitational pull of the star – for very long times, before their cores compacted.

At some point, the compacting of the cores inevitably led to massive implosions that gave birth to black holes. What the team determined in the new study is that each such event may have initially produced two small black holes at the core of each supermassive star, which then merged to create a larger structure.

“This is a new finding. Nobody has ever predicted that a single collapsing star could produce a pair of black holes that then merge,” Reisswig adds. Details of the new study were published in an October issue of the esteemed scientific journal Physical Review Letter.