2019 Nobel Prize in Physics Awarded for Discovery of Exoplanet Orbiting a Solar-type Star

Michel Mayor and Didier Queloz have been awarded the 2019 Nobel Prize in Physics for the discovery of the first exoplanet around a Sun-like star. Mayor, Professor Emeritus at Geneva University in Switzerland, and Queloz, Professor of Physics at the Cavendish Laboratory, Cambridge, UK, share the prize “for contributions to our understanding of the evolution of the universe and Earth’s place in the cosmos” with James Peebles, Albert Einstein Professor Emeritus of Science at Princeton University, US.

“ESO is really proud of the Nobel Prize in Physics awarded to Michel Mayor and Didier Queloz for having pioneered a new field in astronomy with the discovery of 51 Pegasi b and many more exoplanets after.” says ESO Director General Xavier Barcons. “The partnership that ESO cultivates with research institutions in the Member States for the development of the most challenging instruments has been key to enable many of these discoveries. In particular HARPS on the ESO 3.6-metre telescope in La Silla Observatory and more recently ESPRESSO on the Very Large Telescope in Paranal are leading the world in radial-velocity searches of planets around stars outside the Solar System. ESO celebrates that two outstanding members of its scientific community, with very strong commitment to ESO, and very successful use of our facilities, have been given this well-deserved recognition.” 

The discovery of 51 Pegasi b, the first exoplanet ever found around a Sun-type star, was announced on 6 October 1995 by Mayor and Queloz, who detected it using the ELODIE spectrograph at the Observatoire de Haute-Provence in France. The discovery revolutionised astronomy, initiating an entirely new field and new instruments focused on finding and characterising exoplanets. The success of ELODIE led to the construction of CORALIE, an improved version of ELODIE mounted on the 1.2-metre Swiss Euler Telescope at ESO’s La Silla Observatory in Chile. The knowledge gained from building and operating these two instruments was put in the development of HARPS, the High Accuracy Radial velocity Planet Searcher, which began operations in 2003. The light from 51 Pegasi b was also observed by HARPS, which performed the first-ever spectroscopic detection of visible light reflected off an exoplanet.

Mayor and Queloz were instrumental in developing the revolutionary radial velocity technique that is still used to search for exoplanets today. This method looks for tiny backwards and forwards motion of the central star, due to the changing direction of the gravitational pull from an (unseen) orbiting exoplanet. If the star is moving towards us, its spectrum is blueshifted, and redshifted correspondingly when it moves away from us. By looking for regular shifts in the spectrum of the star — and so measuring any velocity changes — any periodic effects due to the influence of a companion can be seen.

Both Mayor and Queloz have long-standing collaborations with ESO and have been involved with the organisation’s governing and advisory bodies. They are very experienced observers, having participated in hundreds of observing runs at ESO with a variety of instruments. In 1996, ESO commemorated Mayor and Queloz’s groundbreaking 1995 paper by placing it in a time capsule that is still buried in the wall of the VLT enclosure. It is a testament to the rigour and determination of their work that their discovery is being recognised with a Nobel Prize in Physics over twenty years later.

Courtesy of European Southern Observatory