Added 1 new A* page:NASA just linked a poetically titled Chandra article, X-rays Spot Spinning Black Holes Across Cosmic Sea, talking about conclusions researchers have been able to reach by studying active, distant supermassive black holes, whose X-ray emissions they've been able to see—multiplied several times, kaleidoscope-like—thanks to gravitational lensing.|
"The researchers then used the property that a spinning black hole is dragging space around with it and allows matter to orbit closer to the black hole than is possible for a non-spinning black hole. Therefore, a smaller emitting region corresponding to a tight orbit generally implies a more rapidly spinning black hole."
The X-rays from one of the black holes they observed had such a small cross section that the researchers calculated that the hole's event horizon is spinning at or very near the maximum speed: the speed of light.
"The researchers think that these supermassive black holes likely grew by accumulating most of their material over billions of years from an accretion disk spinning with a similar orientation and direction of spin, rather than from random directions. Like a merry-go-round that keeps getting pushed in the same direction, the black holes kept picking up speed."