A black hole is a region of spacetimeexhibiting such strong gravitationaleffects that nothing—including particlesand electromagnetic radiation such as light—can escape from inside it.[1] The theory of general relativity predicts that a sufficiently compact mass can deformspacetime to form a black hole.[2][3] The boundary of the region from which no escape is possible is called the event horizon. Although crossing the event horizon has enormous effect on the fate of the object crossing it, it appears to have no locally detectable features. In many ways a black hole acts like an ideal black body, as it reflects no light.[4][5] Moreover, quantum field theory in curved spacetime predicts that event horizons emit Hawking radiation, withthe same spectrum as a black body of a temperature inversely proportional to its mass. This temperature is on the order of billionths of a kelvin for black holes of stellar mass, making it essentially impossible to observe.
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