Our black hole may be sleeping now...

摘要

If galileo or Newton had invented a top-notch gamma-ray telescope in the mid-1600s, they might have witnessed a dazzling display of gamma rays from the colossal black hole at the centre of our galaxy. The finding, based on observations by a space telescope, suggests that the black hole might flare up again in the future, though no one quite knows when. The Milky Way, like most big galaxies, harbours a supermassive black hole at its centre. And although black holes are dark bodies from which even light cannot escape, material swirling towards them becomes extremely hot and starts emitting energetic radiation. This "accretion disc" supplies energy for a whole range of super-bright active galaxies.