Washington: Astronomers have used NASA’s Chandra X-ray Observatory and the European Space Agency’s (ESA’s) XMM-Newton to show a supermassive black hole six billion light-years from Earth is spinning extremely rapidly.
Black holes are defined by just two simple characteristics: mass and spin. While astronomers have long been able to measure black hole masses very effectively, determining their spins has been much more difficult.
Rubens Reis of the University of Michigan in Ann Arbor, who led a paper describing this result, and his colleagues determined the spin of the supermassive black hole that is pulling in surrounding gas, producing an extremely luminous quasar known as RX J1131-1231 (RX J1131 for short).
Because of fortuitous alignment, the distortion of space-time by the gravitational field of a giant elliptical galaxy along the line of sight to the quasar acts as a gravitational lens that magnifies the light from the quasar.
Co-author Mark Reynolds also of Michigan said that because of this gravitational lens, we were able to get very detailed information on the X-ray spectrum – that is, the amount of X-rays seen at different energies – from RX J1131.
He said that this in turn allowed us to get a very accurate value for how fast the black hole is spinning.
The discovery that the black hole in RX J1131 is spinning at over half the speed of light suggests this black hole, observed at a distance of six billion light-years, corresponding to an age about 7.7 billion years after the Big Bang, has grown via mergers, rather than pulling material in from different directions.
The study has been published online in the journal Nature.