A depiction of a black hole

A Black hole is an object that is so massive or so condensed that the escape velocity from its gravity, within a radius known as the event horizon, is greater than lightspeed.

Since not even light can escape from a black hole, they cannot be detected directly, but only by their effects on their surroundings. For instance, stars and other luminous objects may orbit around black holes. A star must be at least three solar masses for a black hole to form naturally by gravitational collapse, much smaller objects could in theory be compressed into black holes by extreme compression.

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