A Doughnut Near a Black Hole

We study black holes not just by looking at the stars in orbit around them, but also by looking at their emissions. Stuff that's closer to the black hole than actual stars is this accretion disk,. It's filled with gas that's really, really hot and giving off all sorts of particles and x rays. Some of these guys emit very, very bright beams of light, sort of up and down along their spin axes. And quasars are actually the reason that web ed black holes exist in the first place.