WASHINGTON—At the center of the Milky Way galaxy resides a supermassive black hole four million times the mass of our sun called Sagittarius A* that some scientists have called a gentle giant because of its quiescence. But someday it could become a beast.
Researchers said on Tuesday they have observed in real time a dramatic brightening at the heart of another galaxy apparently caused by a supermassive black hole awakening from dormancy and beginning to gorge itself with nearby material. It marks the first time this awakening process has been seen as it happens.
