The Milky Way's black hole (in the galactic centre) is unusually quiet - is a supernova from 10,000 years ago the reason? Cosmiverse and NASA report:

"Ten thousand years ago a supernova exploded very close to Sagittarius A*. The fast-expanding gases swept away much of the local interstellar gas and dust, preventing material from falling into the Milky Way's supermassive black hole, thereby starving it. Less material falling into the black hole meant fewer X-rays being emitted"

But then again, could it more like a dormant volcano. In 2001:

"Sagittarius A* suddenly brightened. Within minutes it was 45 times its normal intensity. Then it faded back to its pre-flare level about three hours later".