Hawking radiation is the quantum radiation predicted by Stephen Hawking in 1974 to be emitted by black holes.
In quantum field theory curved by gravity, the vacuum near a black-hole event horizon is not completely featureless to distant observers. The resulting calculation shows that a black hole can emit thermal radiation with a temperature determined by its mass, angular momentum, and electric charge. For a nonrotating, uncharged black hole, the temperature is inversely proportional to its mass.
This prediction transformed the understanding of black holes. They are not perfectly black in quantum theory and can gradually lose mass. Smaller black holes are hotter and radiate more strongly, while astrophysical black holes are expected to be extremely cold.
Hawking radiation is often explained using particle–antiparticle pairs appearing at the horizon, but that picture is only a simplified heuristic. The rigorous prediction comes from quantum field theory in curved spacetime. Hawking radiation has not yet been directly observed from an astrophysical black hole.