Black hole

Summary

A black hole is a region of spacetime from which nothing, not even light, can escape to far-away observers. Its boundary is the event horizon. In general relativity black holes form by gravitational collapse, as in the Oppenheimer–Snyder model. By the no-hair theorem the stationary ones in electrovacuum are described by the Kerr–Newman metric family. Black holes are central objects of both mathematical relativity and astrophysics.