Black holes form when a star more than ten times the size of the Sun explodes or a giant clump of mass comes together and forms to a black hole. Black holes are predicted by general relativity. Under the description provided by general relativity, as an object moves closer to a black hole, the energy required for it to escape continues to increase until it becomes infinite at the event horizon, the surface beyond which escape is impossible. Inside the event horizon. At the center of a black hole is the singularity, a point of zero size and infinite density. The geometry of space-time is distorted in a way that makes moving closer to the central singularity inevitable no matter how the infalling object moves.
The existence of black holes in the universe is well supported by astronomical observation, particularly from studying X-ray emission from X-ray binaries and active galactic nuclei. It has been hypothesised that black holes radiate energy due to quantum mechanical effects known as Hawking radiation. The source of a black hole's immense gravity is the fact that it is extremely massive, yet infinitely small giving it an extremely high density. Stellar-mass black holes are the most common black holes in the universe.
It is theorized that black holes may connect to form a wormhole. If this would happen a black hole would connect to another extremely far away causing a quantum time disperstion effect allowing any spacecraft or matter to theoretically pass through it.