Crash Course Astronomy | Galaxies, part 2: Crash Course Astronomy #39 | Episode 39 | PBS

Active galaxies pour out lots of energy, due to their central supermassive black holes gobbling down matter. Galaxies tend not to be loners, but instead exist in smaller groups and larger clusters. Our Milky Way is part of the Local Group, and will one day collide with the Andromeda galaxy.