Distant Black Hole Spins at Nearly Half the Speed of Light

A newly discovered distant super massive black hole, several billion light years away from Earth, is spinning at almost half the speed of light, according to a new finding.

This is the first time that astronomers have directly measured the spin rate of a distant black hole. This newly measured super massive black hole is located 6.1 billion light years away and is inside a quasar, RX J1131-1231.

The measurement of the black hole's spin was made using NASA's Chandra X-ray Observatory and the European Space Agency's XMM-Newton.

The two basic characteristics of the black holes are the mass and spin.  Though the astronomers succeeded in effectively measuring the mass of the black hole, they found it extremely challenging to determine its spins. 

In this new finding, Rubens Reis along with colleagues at the University of Michigan determined the spin of the supermassive black hole that is producing a luminous quasar dubbed RX J1131-1231 by absorbing the surrounding gas.

Quasars are the distant cosmic objects that are powered by black holes that have billion of times the mass of the Sun. Most of them have been discovered billions of light years away and live only in galaxies with black holes. They are classified as the active galactic nuclei and are known to emit energy of several billion or trillion electron volts.

 The distance of the quasar made it too faint to measure the spin rate. But the researchers overcame the challenge by taking advantage of the natural telescope effect called 'gravitational lensing'. Initially, predicted by Einstein, this natural telescope offers the astronomers the rare opportunity to study the intricate innermost region of the far away quasar by magnifying the light from these sources.

"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," said co-author Mark Reynolds also of Michigan. "This in turn allowed us to get a very accurate value for how fast the black hole is spinning."

When the disk of gas and cosmic dust surrounding the black hole creates a corona, the X rays are produced. These X rays offer a glimpse in to the inner edge of the disk of gas.

"We estimate that the X-rays are coming from a region in the disk located only about three times the radius of the event horizon, the point of no return for infalling matter," said Jon M. Miller of Michigan, another author on the paper. "The black hole must be spinning extremely rapidly to allow a disk to survive at such a small radius."

The measurement of the spin rate is important as this enhances the understanding of how black holes grow over the period of time. Based on the measurements, it seems that the black hole is spinning at approximately half the speed of light suggesting this particular black hole, six billion light years away, was mostly formed 7.7 billion years after the Big Bang.

They also found that the black hole was formed as a result of mergers (galaxy merging with another galaxy) and not by absorbing materials from various directions.

Based on the high spin rate it is estimated the galaxy is absorbing a lot of the material descending on it.