The discovery of 51 Pegasi b was announced in 1995.
Michel Mayor and Didier Queloz detected the planet using the ELODIE spectrograph at the Haute-Provence Observatory in France. Their measurements showed that the Sun-like star 51 Pegasi was undergoing a regular radial-velocity wobble, caused by an orbiting companion. The discovery was announced on 6 October 1995, and the findings were published in Nature later that year.
51 Pegasi b was a landmark because it was the first confirmed exoplanet found orbiting a main-sequence star like the Sun. Earlier planets had been detected around pulsars, including planets orbiting PSR B1257+12, but 51 Pegasi b demonstrated that planets also existed around ordinary Sun-like stars.
The planet was startlingly close to its star, completing an orbit in about 4.23 days. Its unexpectedly short period helped establish the category now called hot Jupiters: giant planets that orbit extremely near their host stars. In 2019, the IAU approved the proper name Dimidium for 51 Pegasi b.