Now there’s a look in your eyes, like black holes in the sky

The economist

The universe’s darkest denizens are being dragged into the light

Jan 9th 2016  | KISSIMMEE, FLORIDA | From the print edition

http://goo.gl/SvReMA

(copy)

Working out how black holes affect galactic growth, though, is not the same as finding out what is happening in the vicinity of the holes themselves. Here, matter is circling close to a black hole’s point of no return, the “event horizon” whose radius was described by Schwarzschild’s calculations. And next month, JAXA, Japan’s space agency, will launch Astro-H, a telescope that will help to do this. It can detect X-rays of exceptionally high energies. As material slips ever closer to the event horizon, the precise details of its X-ray output are a signal of how it is moving. Astro-H will be able to measure this radiation, and thus infer that motion with unprecedented precision. This will permit researchers to measure unambiguously, for the first time, how fast a black hole is spinning. That, in turn, permits tests of Einstein’s general theory of relativity—the very theory that Schwarzschild used to put black holes on solid mathematical ground—that have remained out of reach until now.