Discovery of 51 Pegasi b

51 Pegasi b was the first planet found orbiting a Sun-like star outside our Solar System. It was detected by the Swiss astronomers Michel Mayor and Didier Queloz at the Haute-Provence Observatory in France, who measured tiny periodic shifts in the light of the star 51 Pegasi caused by the gravitational tug of an unseen companion. The planet is comparable in mass to Jupiter but orbits its star in only about four days, far closer than Mercury is to the Sun. It was the first example of a hot Jupiter, a type that surprised astronomers, who had not expected giant planets so near their stars. Mayor and Queloz shared the 2019 Nobel Prize in Physics for the discovery.

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