Discovery of the First Exoplanet, 51 Pegasi b

On October 6, 1995, Swiss astronomers Michel Mayor and Didier Queloz announced their groundbreaking discovery of 51 Pegasi b, the first confirmed exoplanet orbiting a Sun-like star. This landmark event took place at the University of Geneva, where the two scientists were conducting research.

Context and Discovery

• Background: Before this discovery, the existence of planets outside our solar system was purely theoretical. While planets had been found orbiting pulsars in the early 1990s, 51 Pegasi b was the first to be discovered orbiting a star similar to our Sun.

• The Star: The exoplanet was found orbiting 51 Pegasi, a G-type main-sequence star located approximately 50 light-years away in the constellation Pegasus. This star closely resembles our own Sun in terms of size and temperature.

• Methodology: Mayor and Queloz employed the radial velocity method to detect the exoplanet. This technique involves measuring the Doppler shifts in the star’s spectrum, which indicate gravitational interactions with an orbiting planet.

Characteristics of 51 Pegasi b

• Classification: 51 Pegasi b is a ‘Hot Jupiter’, a class of exoplanets characterized by their large mass and close proximity to their parent stars.

• Orbit and Climate: It orbits its star every 4.2 days. Due to its close orbit, the planet is intensely heated by its star, leading to extreme atmospheric conditions.

Impact and Significance

• Astronomical Milestone: The discovery of 51 Pegasi b marked a pivotal point in astronomy, proving that planets similar to those in our solar system exist around other stars, thus opening new frontiers in the search for extraterrestrial life.

• Recognition: In 2019, Michel Mayor and Didier Queloz were awarded the Nobel Prize in Physics for their discovery, acknowledging the profound impact their work had on the field of astronomy.

• Legacy: This discovery paved the way for the detection of thousands of exoplanets, transforming our understanding of the universe and the potential for discovering Earth-like planets.

This historic announcement on October 6, 1995, fundamentally changed our conception of the cosmos by highlighting the ubiquity of planetary systems beyond our own.