Supermassive Black Hole's Spin Revealed for First Time by NASA

Black holes have remained enigmatic for years. Yet now, NASA has teamed up with the European Space Agency to measure definitively, for the first time, the spin rate of a black hole with a mass two million times that of our sun.

The massive black hole that the researchers measured is located at the heart of a gas- and dust-filled galaxy known as NGC 1365. Like other supermassive black holes, it was surrounded by pancake-like accretion disks, formed as its gravity pulled matter inward. Einstein's theory predicts that the faster a black hole spins, the closer the accretion disk lies to the black hole and the more the X-ray light streaming off the disk will be warped.

"These monsters, with masses from millions to billions of times that of the sun, are formed as small seeds in the early universe and grow by swallowing stars and gas in their host galaxies, merging with other giant black holes when galaxies collide, or both," said the study's lead author, Guido Risaliti, in a press release.

In order to actually measure the spin of the black hole, though, the agencies had to employ NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) and the European Space Agency's XXM-Newton. They traced matter as it swirled into the black hole by using X-rays emitted from regions very close to the black hole. The radiation that they saw was warped and distorted by the motions of the particles and the black hole's gravity.

Before now, these measurements were almost impossible. Clouds of gas obscured the black holes and confused any results. Yet with the help of XXM-Newton, NuSTAR could  see a broader range of X-ray energies and could penetrate deeper into the region around the black hole. In fact, the new data demonstrated that the X-rays were not warped by the clouds, but were instead warped by the tremendous gravity associated with the black hole.

So exactly how fast was the black hole spinning? They found that the black hole was spinning almost as fast as Einstein's theory of gravity will allow. The findings resolved a long-standing debate about similar measurements in other black holes and will help lead to a better understanding of how black holes and galaxies evolve.

The research is published in the journal Nature.