Last year, scientists used gravitational waves to detect an elusive intermediate-mass black hole for the first time. Now, Australian astronomers have spotted another – this time using gamma-ray bursts.
Black holes are formed when massive stars reach the end of their lives and collapse under their own gravity. But they aren’t all the same – stellar mass black holes are small, just a few times the mass of our Sun, while supermassive black holes at the hearts of galaxy are enormous, with masses millions or even billions of times greater than our sun.
Intermediate mass black holes are the missing link between these two populations, thought to span between 100 and 100,000 solar masses. The black hole discovered in 2020 was 142 solar masses – while this newly discovered monster is on the other end of the scale, at approximately 55,000 solar masses.
The study, published in Nature Astronomy, describes detecting the black hole through a gamma-ray burst – a flash of high-energy light emitted when two distant stars collided. But the researchers observed not one but two of these bursts reaching their detectors, because the signal had been gravitationally lensed by a massive object somewhere between the collision and Earth. The object – the black hole – distorted space time, producing multiple images of the same event.
This discovery could help astronomers understand how supermassive black holes form and grow as large as they do.
“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,” explains study co-author, 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.”
The study estimates that there are around 46,000 black holes of this mass in our neighbourhood of the Milky Way alone.
Lauren Fuge is a science journalist at The Royal Institution of Australia.
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