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…
