Black Hole

A black hole is an object with a gravitational field so strong that its escape velocity (the speed of an object leaving the gravitational field) exceeds the speed of light. In other words, not even light can escape the gravitational field of a black hole, and therefore no light is emitted from it. Since no light is emitted, it is a 'black' hole in space.

Black holes are part of the Einstein's predictions of general relativity.