The 1995 exoplanet found by detecting Doppler shifts in 51 Pegasi is 51 Pegasi b. The planet was identified from the star’s small, periodic radial-velocity wobble rather than by seeing the planet directly.
Michel Mayor and Didier Queloz announced the discovery on October 6, 1995, using the ELODIE spectrograph at France’s Haute-Provence Observatory. The instrument measured stellar spectral-line shifts of roughly 70 metres per second, revealing the gravitational tug of an orbiting companion.
51 Pegasi b was the first confirmed planet found orbiting a Sun-like main-sequence star, although planets had previously been detected around pulsars. Its roughly 4.23-day orbit is extremely close to its star, making it the prototype of the “hot Jupiter” class.
A common mix-up is confusing the planet with 51 Pegasi, which is the host star. The planet was later given the approved name Dimidium, but 51 Pegasi b remains its standard scientific designation.