Black hole once glowed brightly

Fluorescing clouds provide clues to its former glory

A little more than 26,000 years ago, a sleeping giant at the center of our galaxy suddenly awoke, spewed several pulses of X-rays and went back into hibernation.

That’s the conclusion of a long-term X-ray study of large gas clouds near the Milky Way’s central, supermassive black hole — a 4-million-solar-mass monster dubbed Sagittarius A*.