Black hole
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of hot plasma orbiting a black hole (from NASA)]]A classical black hole is a theoretical concentration of mass with a gravitational field so strong that its escape velocity exceeds the speed of light. This implies that nothing, even light can escape its gravity, hence the term black. The name black hole is very widespread, even though the theory does not refer to any hole in the usual sense.
According to classical general relativity, no matter or information can flow from the interior of a black hole to an outside observer (e.g. one cannot bring out some of its mass, or light it up with a light source such as a flashlight, or retrieve any information about the material that has entered the black hole), although quantum mechanics may allow deviations from this strict rule. The existence of black holes in the universe is well supported both theoretically and by astronomical observation; however, a small minority of physicists dissent.