What is a black hole?

A black hole is a region in space where gravity is so strong that nothing, not even light, can escape from it. Black holes form when very massive stars use up all their fuel and collapse under their own gravity during a supernova explosion. The massive gravity pulls everything inward, creating a point called a singularity. No information or matter can get out once it goes inside. Black holes are invisible and can only be detected by observing their effects on nearby stars or gas. They are among the most mysterious and fascinating objects in the universe.