For the first time ever, scientists say they have conclusively measured the rate at which a supermassive black hole spins. And like all things related to black holes, the results are predictably mind-bending: The surface of the black hole at the center of the galaxy NGC 1365 is traveling at nearly light speed, according to the results of a new study made using space telescopes from NASA and the European Space Agency.
Determining the black hole's spin rate in terms of an exact numeric velocity, like how speed works on Earth, is challenging because spinning black holes distort spacetime around them. "It's not like we can paint a little dot on the black hole and watch it spin around at some velocity," said Fiona Harrison, a Caltech astrophysicist in charge of NASA's Nuclear Spectroscopic Telescope Array (NuSTAR), in a press conference held Wednesday on the find.
equivalent to a billion stars shining over the course of a billion years
That said, scientists do know how much energy is given off by this black hole's rotational energy, equivalent to a billion stars shining over the course of a billion years. Scientists also know to what extent the black hole's spin is distorting spacetime. "If you were standing near the event horizon of this particular black hole, you would have to turn around once every four minutes just to stand still," Harrison said.
The supermassive black hole examined in this study has a mass two million times our Sun and its galaxy is located 60 million light years from Earth. Most galaxies are thought to have supermassive black holes at their center. But until now, scientists have only been able to estimate how fast they are spinning because clouds of gas block some of the view. NASA's NuSTAR telescope, launched into space last summer, takes a broader view of high-energy x-rays being emitted by the matter that gets sucked into a black hole. The new findings should help verify previous measurements of other smaller black hole spin rates, according to NASA.