Astronomy: Early Universe explosion sheds light on elusive black hole

Distorted light from an explosion that occurred when the Universe was three billion years old may have revealed an intermediate-mass black hole, a paper in Nature Astronomy suggests. These findings could have implications for understanding of black hole formation and of how low-mass black holes become supermassive black holes.

Intermediate-mass black holes are thought to be an evolutionary midpoint between their low- and high-mass counterparts, but observational evidence for their existence has been scarce and inconclusive. Measuring how many intermediate-mass black holes exist could provide clues to understanding how black holes form and grow with time.

James Paynter, Rachel Webster and Eric Thrane analysed thousands of γ-ray bursts (luminous explosions following the violent collapse of a star or the merger of two stars) to look for signs of gravitational lensing, which occurs when an object — acting as a lens — intercepts the emission of these faraway explosions and distorts it, creating multiple images that are observed at different times. This time delay is important in identifying the existence of dark ‘objects’ that would otherwise remain invisible. The authors identify a γ-ray burst event that showed evidence of gravitational lensing and estimate that the intervening object had a mass of around ten thousand solar masses, making it a good candidate for an intermediate-mass black hole.

Further research and detections will be needed to understand the abundance of these elusive black holes and their implications for the evolution of other black hole populations.

doi: 10.1038/s41550-021-01307-1

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