Newly discovered black hole could have formed 'before the first stars and galaxies' © Carl Knox/OzGrav/PA

Newly discovered black hole could have formed ‘before the first stars and galaxies’

Researchers observed the same pair of merging stars twice: once directly, and once as an 'echo' caused by the black hole.

A newly discovered black hole approximately 55,000 times the mass of the Sun could be an ancient relic created before the first stars and galaxies formed, scientists have said.

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Such a black hole may be the seed of the supermassive black holes which exist today and could help scientists estimate the total number of these objects in the Universe, researchers said.

The discovery of the “intermediate-mass” or “Goldilocks” black hole – different to the small black holes made from stars and the supermassive giants in the core of most galaxies – is published in the journal Nature Astronomy.

Researchers estimate that there are some 46,000 intermediate-mass black holes in the vicinity of the Milky Way galaxy. The new black hole was discovered by researchers from the University of Melbourne and Monash University, through the detection of a gravitationally lensed gamma-ray burst.

The burst – a half-second flash of high-energy light emitted by a pair of merging stars – had an “echo”, caused by the intermediate-mass black hole, which bent the path of the light on its way to Earth so that astronomers saw the same flash twice.

Software developed to detect black holes from gravitational waves was adapted to show that the two flashes were images of the same object.

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“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 study co-author, Professor Eric Thrane, from Monash University. “These early black holes may be the seeds of the supermassive black holes that live in the hearts of galaxies today.”

Fellow paper co-author Professor Rachel Webster, from the University of Melbourne, described the findings as “exciting”.

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“Using this new black hole candidate, we can estimate the total number of these objects in the Universe,” she said. “We predicted that this might be possible 30 years ago, and it is exciting to have discovered a strong example.”

Reader Q&A: How big could a black hole get?

Asked by: Vanessa Taylor, Nottingham

There is no theoretical upper limit to the mass of a black hole. However, astronomers have noted that the ultra-massive black holes (UMBHs) found in the cores of some galaxies never seem to exceed about 10 billion solar masses. This is exactly what we’d expect from the rate at which we know black holes grow, given the time that’s elapsed since the Big Bang.

Furthermore, recent studies suggest that UMBHs cannot physically grow much beyond this anyway, since they would then begin to disrupt the accretion discs that feed them, choking the source of new material.

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