As the earliest black hole seen in X-rays, it could reveal how these mammoths grow so large.
NASA’s Chandra X-ray Observatory and the James Webb Space Telescope discover the most distant black hole ever seen with X-rays.
Dating from just 470 million years after the Big Bang, the find gives strong weight to the theory that supermassive black holes start their lives large in size, rather than growing over time.
The black hole, located in the galaxy UHZ1, was initially found in the infrared by the Webb Telescope, with later observations from Chandra finding strong X-ray emissions.
“We needed Webb to find this remarkably distant galaxy and Chandra to find its supermassive black hole,” says Akos Bogdan from the Center for Astrophysics, Harvard and Smithsonian, who led the study.
“We also took advantage of a cosmic magnifying glass that boosted the amount of light we detected.”
Gravitational lensing
The magnification used to discover the black hole was an effect known as gravitational lensing.
The light from UHZ1 was bent by the gravity of a galaxy cluster closer to Earth.
This magnifies the image, similar to if the light had passed through a lens, and allowed Chandra to detect the galaxy’s X-ray emission.
This showed the presence of superheated gas – a tell-tale sign that a supermassive black hole lies at the centre.
How did the black hole get so big?
Such early black holes are a boon for those seeking to answer one of cosmology’s biggest questions: how did supermassive black holes grow so large?
The two leading theories are that they either began as small black holes, 10 to 100 times the size of our Sun, or they were born already weighing 10,000 to 100,000 solar masses.
UHZ1’s black hole seems to be 10 to 100 million solar masses, around the same mass as all the stars in the galaxy where it lives, combined.
For comparison, nearby supermassive black holes are only 0.1% the mass of their host galaxy’s stars.
UHZ1 could be an example of an ‘Outsize Black Hole’, an idea first proposed by Priyamvada Natarajan from Yale University in 2017, whereby supermassive black holes form directly from the collapse of a huge cloud of gas.
“We think that this is the first detection of an ‘Outsize Black Hole’ and the best evidence yet obtained that some black holes form from massive clouds of gas,” says Natarajan.
“For the first time we are seeing a brief stage where a supermassive black hole weighs about as much as the stars in its galaxy, before it falls behind.”