Astronomers have found the most distant black hole ever confirmed, at more than 31 billion light years from Earth. This object and others like it could finally settle the question of how supermassive black holes got so enormous so quickly in the early universe.
at Yale University and her colleagues spotted the galaxy UHZ-1 in data from the James Webb Space Telescope (JWST). They then pointed the Chandra X-ray Observatory in the same direction to confirm the presence of a supermassive black hole at the centre of the galaxy.
鈥淢any distant black holes are being detected and claimed with James Webb data, but the special thing with this one is to really confirm and pin it down,鈥� says Natarajan. 鈥淴-ray has always been the way we know for sure that we have a black hole 鈥� it鈥檚 dead cert, no ambiguity.鈥� No other black hole this distant has ever been confirmed with X-rays before.
Advertisement
The extreme distance to UHZ-1 means that we are observing it as it was about 470 million years after the big bang, when the universe was only about 3 per cent of its current age. The light traveled about 13.2 billion light years to get to Earth, but the expansion of the universe means that the galaxy is now more than 31 billion light years away. The observations indicate that the black hole probably has a mass between 10 million and 100 million times the mass of the sun.
The combination of an early formation time and a huge mass makes this black hole particularly challenging to explain using traditional models of the formation of supermassive black holes. If it began as a star, which collapsed in on itself to become a black hole, it is hard to imagine how it could have gotten so massive in such a short period of time 鈥� even if the star was a particularly colossal one.
In recent decades, another possible formation mechanism has emerged: if enough gas flowed into the centre of a galaxy and then collapsed directly into a black hole, you could create a much heavier 鈥渟eed鈥� for a supermassive black hole to grow from. These heavy seeds could reach hundreds of thousands of solar masses, whereas the lighter seeds formed from stars couldn鈥檛 get heavier than about 100 solar masses.
This black hole is one of the strongest pieces of evidence yet for the direct collapse model and the existence of heavy black hole seeds. 鈥淚f it starts from a seed of roughly 10,000 solar masses then we can reach the mass that we see in UHZ-1 very comfortably, with no extra constraints or caveats,鈥� says Natarajan. 鈥淭his satisfies all of the requirements for being a heavy seed.鈥�
But satisfying all of the requirements does not make it a certainty, says at the Harvard-Smithsonian Center for Astrophysics in Massachusetts. 鈥淚f this is at a 100 million solar masses it鈥檚 pretty big, but if it鈥檚 at 10 million solar masses it鈥檚 not that big, so it could have possibly formed from a lighter seed,鈥� he says. 鈥淓verything hinges on finding more of these objects, possibly more massive, possibly at even higher distances, to really understand how the first population of black holes formed.鈥�
The good news is that JWST is uniquely equipped to find these black holes, and Chandra to confirm them, so those discoveries are likely to happen relatively soon, says Pacucci.
Journal references:
Nature Astronomy ,
The Astrophysical Journal Letters
