What makes astronomers think there are black holes in space?
1.When galaxies dissapear, they stop emitting infrared radiation, and a hole in space is formed
2.There are areas of space from which no electromagnetic energy of any kind has been deleted
3.At the end of a star's life cycle, it runs out of hydrogen and stops emitting visible light
4.Bursts of light that release large amounts of radio waves precede the formation of a black hole