NASA puts new spin on black holes

By Charis Palmer, The Conversation

Using data taken by the Nuclear Spectroscopic Telescope Array, or NuSTAR, and the European Space Agency's XMM-Newton X-ray satellite, scientists were able to measure the spin rate of a black hole with a mass 2 million times that of our sun.

NASA said the observations, which are published in the journal Nature, provide a powerful test of Einstein's theory of general relativity, which says gravity can bend space-time, the fabric that shapes our universe, and the light that travels through it.

“We can trace matter as it swirls into a black hole using X-rays emitted from regions very close to the black hole,” said NuSTAR principal investigator Fiona Harrison of the California Institute of Technology. “The radiation we see is warped and distorted by the motions of particles and the black hole's incredibly strong gravity.”

A similar experiment was undertaken in 2006, said Geraint Lewis, professor of astrophysics at University of Sydney. “But there was a worry intervening gas could have distorted the shape of the emission and therefore we weren't accurately measuring the spin.” Professor Lewis said the new research found that the measurements wouldn't have been so badly affected. “It's confirmed that these black holes are spinning and they're spinning very fast.”

The researchers said while XMM-Newton revealed that light from the iron was being warped, NuSTAR proved that this distortion was coming from the gravity of the black hole and not gas clouds in the vicinity. “The next thing they surely will do now is go and look at a range of galaxies to see if they can measure the spin there,” Professor Lewis said. “If we found a large number that weren't spinning it would be a serious problem for our understanding of the galaxy.”

“This is hugely important to the field of black hole science,” said Lou Glassiness, a NuSTAR program scientist at NASA Headquarters in Washington.