“This newly discovered black hole could be an ancient relic—a primordial black hole—created in the early Universe before the first stars and galaxies formed,” said Eric Thrane from the Monash University School of Physics and Astronomy and Chief Investigator for the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav). The discovery of a ‘Goldilocks’ black hole is part of a missing link between two populations of black holes. “These early black holes may be the seeds of the supermassive black holes that live in the hearts of galaxies today.”
One of 46,000 intermediate-mass black holes in the Milky Way Galaxy
“We know very well that black holes can be formed by the collapse of large stars, or as we have seen recently, the merger of two neutron stars,” said Savvas Koushiappas, a physicist at Brown University, who was not involved in the study. With future gravitational wave experiments, we’ll be able to look back to a time before the formation of the first stars to see if black hole merger events existed before stars formed in the cosmos. Then we’ll know that those black holes are not of stellar origin. ”It’s been hypothesized that there could be black holes that formed in the very early universe before stars existed at all.”
In a joint effort, researchers from the University of Melbourne and Monash University have uncovered a black hole approximately 55,000 times the mass of the sun, a fabled “intermediate-mass” black hole. It is one of some 46,000 expected intermediate-mass black holes in the vicinity of our Milky Way galaxy.
Gargantuan Size an Enigma
“While we know that these supermassive black holes lurk in the cores of most, if not all galaxies, we don’t understand how these behemoths are able to grow so large within the age of the Universe,” said Lead author and University of Melbourne Ph.D. student, James Paynter. The detection of a gravitationally lensed gamma-ray burst — a half-second flash of high-energy light emitted by a pair of merging stars — was observed to have a tell-tale ‘echo’. This echo is caused by the intervening intermediate-mass black hole, which bends the path of the light on its way to Earth, so that astronomers see the same flash twice. Software developed to detect black holes from gravitational waves was adapted to establish that the two flashes are images of the same object.
“Using this new black hole candidate, we can estimate the total number of these objects in the Universe. We predicted that this might be possible 30 years ago, and it is exciting to have discovered a strong example,” said gravitational lensing pioneer, Rachel Webster from the University of Melbourne.
Source: Evidence for an intermediate-mass black hole from a gravitationally lensed gamma-ray burst, Nature Astronomy (2021). DOI: 10.1038/s41550-021-01307-1
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