Distant Black Hole Spin Measured by Astronomers


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Astronomers this week revealed that the spin of a very distant black hole has been directly measured. The new measurement is part of a new report published this week in the journal Nature and should help cosmologists further investigate the characteristics and evolution of black holes.

The spin of black hole/quasar RX J1131-1231 was measured by University of Michigan astronomer Rubens Reis and his colleagues. The object resides around six billion light years from our solar system, making the measurement more difficult. Previously only black holes up to 4.7 billion light years away had had their spin measured.

The researchers were able to measure the spin of this specific black hole due to its specific location. The line-of-sight to the black hole from Earth passes through a giant galaxy that acts as a gravitational lens. This allowed the astronomers to study RX J1131-1231 as if it were much closer than it is.

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

According to NASA, the spin of a black hole can help astronomers determine how a black hole has grown in the past and how it may evolve into the future. RX J1131-1231 was measured as spinning very rapidly at over half the speed of light.

Image courtesy NASA/CXC/Univ of Michigan/R.C.Reis et al/STSc