Pegasus is the winged horse of Greek myth, and his origin is told by Hesiod: when Perseus struck off the head of the Gorgon Medusa, Pegasus and the warrior Chrysaor sprang from her blood or her severed neck, born beside the streams of Ocean, a birth from violence and from the monstrous. His name was linked by the ancients to the springs (pegai) at which he was born. Tamed at last by the hero Bellerophon with a golden bridle given by Athena, Pegasus carried him into the air to kill the fire-breathing Chimera from above, out of reach of its flames.
Pegasus was set among the stars as one of the larger northern constellations, and its most recognisable feature, the Great Square of Pegasus, formed by four bright stars, is one of the standard reference asterisms amateur astronomers use to navigate the autumn sky; one corner of the square is technically shared with the neighbouring constellation Andromeda rather than belonging to Pegasus alone, a quirk of the traditional boundaries drawn between the two figures. Pegasus's constellation lent its name to modern astronomy in an unexpected way: the star 51 Pegasi, in the same constellation, was found in 1995 to be orbited by a planet, 51 Pegasi b, the first exoplanet ever confirmed around a Sun-like star, a discovery that won its finders the 2019 Nobel Prize in Physics and that briefly carried the working nickname Bellerophon before being formally named Dimidium.