NASA | X-ray 'Echoes' Probe Habitat of Monster Black Hole
Astronomers using data from the European Space Agency's XMM-Newton satellite have found a long-sought X-ray signal from NGC 4151, a galaxy that contains a supermassive black hole. The discovery promises a new way to unravel what's happening in the neighborhood of these powerful objects. Most big galaxies host a big central black hole containing millions of times the sun's mass. When matter streams toward one of these supermassive black holes, the galaxy's center lights up, emitting billions of times more energy than the sun. For years, astronomers have been monitoring such "active galactic nuclei" (AGN) to better understand what happens on the brink of a monster black hole. Matter falling toward a black hole collects into a rotating disk, where it becomes compressed and heated before eventually spilling over the black hole's event horizon, the point beyond which nothing can escape and astronomers cannot observe. A mysterious and intense X-ray source near the black hole shines onto the surface layers of the accretion disk, causing iron atoms to radiate characteristic emission -- what astronomers call the iron K line -- at about 6000 to 7000 electron volts. The inner part of the disk is orbiting the black hole so fast that the effects of Einstein's relativity come into play -- most notably, how time slows down close to the black hole. These relativistic effects broaden and distort the X-ray signal in a unique way. When the X-ray source near NGC 4151's black hole flares up <b>...</b>
Scott Wiessinger NASA x-ray Goddard Goddard Space Flight Center black hole satellite galaxy space
