Astronomers Find a Planet Around a Sun-like Star

On October 6, 1995, Michel Mayor and Didier Queloz of the University of Geneva announced the detection of a planet orbiting 51 Pegasi, a main-sequence star roughly fifty light-years from Earth in the constellation Pegasus. Announcing the find at a conference in Florence, Italy, and later publishing it in the journal Nature, the Swiss astronomers revealed that a companion body was circling a star fundamentally similar to the Sun. Their discovery marked the first confirmed detection of an extrasolar planet around a solar-type star, initiating an unprecedented era in observational astronomy and altering the scientific pursuit of planetary systems.

The identification of the world, formally cataloged as 51 Pegasi b, relied on the radial velocity technique using the ELODIE spectrograph at the Haute-Provence Observatory in France. This instrument measured minute, cyclical variations in the star's spectral lines, revealing shifts in velocity of about 59 meters per second. These subtle wobbles were induced by the gravitational influence of the unseen companion, which orbited only about eight million kilometers away from its host star. By mid-October, astronomers Geoffrey Marcy and Paul Butler at the Lick Observatory in California had independently confirmed the signal.