Astronomers making use of a phenomenon known as gravitational lensing have discovered a black hole about 33 billion times the mass of the Sun — close to the upper limit of how large scientists believe they can be.
The rare "ultramassive" black hole sits at the centre of Abell 1201, a supergiant elliptical galaxy residing in a galaxy cluster of the same name, about 2.7 billion light-years from Earth.
Researchers from the United Kingdom's Durham University and Germany's Max Planck Institute discovered the black hole using an innovative technique combining supercomputer simulations with high-resolution pictures taken by the Hubble Space Telescope.
The Hubble pictures showed light from another galaxy behind Abell 1201 was reaching Earth in a way that indicated it was bending around an extremely massive object along the way — creating a 'lensing' effect in which the more distant galaxy was both magnified and seemingly multiplied around a curved edge.
Astronomers believe every large galaxy has a black hole of at least supermassive size (more than 100,000 times the mass of the Sun) at its centre.
The researchers used Durham's DiRAC COSMA8 supercomputer to run hundreds of thousands of simulations of light travelling the same path, each time with a black hole of a different mass in the way.
When an ultramassive black hole roughly 33 billion times the mass of the Sun was included in the simulations, they produced images that matched the real pictures taken by Hubble.
Dr James Nightingale was lead author of the group's study, which was published in the scientific journal Monthly Notices of the Royal Astronomical Society on Wednesday.
He called the results of the study "extremely exciting", and said the technique the researchers used had implications for future study on distant black holes.
"This particular black hole, which is roughly 30 billion times the mass of our Sun, is one of the biggest ever detected and on the upper limit of how large we believe black holes can theoretically become," he said.
"Most of the biggest black holes that we know about are in an active state, where matter pulled in close to the black hole heats up and releases energy in the form of light, X-rays, and other radiation.
"However, gravitational lensing makes it possible to study inactive black holes, something not currently possible in distant galaxies. This approach could let us detect many more black holes beyond our local universe and reveal how these exotic objects evolved further back in cosmic time."
The discovery of the Abell 1201 ultramassive black hole answers a question first raised almost 20 years ago by another Durham University astronomer, Professor Alastair Edge, who is listed as one of the study's co-authors.
He was reviewing images of a galaxy survey in 2004 when he first noticed the giant arc of a gravitational lens.
