Quiet Monster

A quiet monster lurks in the heart of M31, the Andromeda Galaxy. Known as M31-star, it’s a black hole a hundred million times the mass of the Sun, and 25 times heavier than the black hole at the heart of the Milky Way. Every large galaxy probably has a supermassive black hole. And many of them are quite bright. The black hole itself is completely black – it swallows up all the matter and energy that falls into it, and nothing can come back out. But the black hole’s gravity pulls in huge amounts of gas and dust, along with an occasional asteroid, star, or other large object. This debris forms a disk around the black hole. As material in the disk spirals closer to the black hole it gets extremely hot, so it shines brightly. But M31-star is one of the quietest of all supermassive black holes – its disk produces very little energy. That tells us that the black hole is not actively “feeding” – not much debris is falling into it. A distant ring of gas and dust encircles the black hole, with filaments of material spiraling into the disk. But the “feeding” rate is low, so M31-star remains quiet – a dark monster in the heart of M31. Under dark skies, the Andromeda Galaxy is visible to the naked eye. It looks like a faint smudge of light that’s wider than the Moon. Right now, it’s about a third of the way up in the east-northeast at nightfall, and climbs high overhead later on. Script by Damond Benningfield