Didier Queloz

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Lore & Background

Queloz was born in Switzerland on 23 February 1966. He studied at the University of Geneva, earning an MSc in physics in 1990, a DEA in Astronomy and Astrophysics in 1992, and a PhD in 1995 under Swiss astrophysicist Michel Mayor. As part of his PhD, he and Mayor discovered 51 Pegasi b, a giant planet orbiting the star 51 Pegasi, detected by measuring small periodic changes in stellar radial velocity using the ELODIE spectrograph at Haute-Provence Observatory. The Daily Telegraph reports him as saying that 'Science inherited a lot from religions.'

Early in his career, Queloz identified stellar activity as a limitation for planet detection and published a reference paper on disentangling stellar activity from planetary signals. He led the installation of the CORALIE spectrograph on the Swiss 1.2-metre Leonhard Euler Telescope and later served as project scientist for the HARPS spectrograph. He achieved the first spectroscopic transit detection of an exoplanet using the Rossiter-McLaughlin effect in 2000, and with his PhD student demonstrated that many planets were surprisingly misaligned or in retrograde orbit. Queloz moved to the University of Cambridge, where he established the Cambridge Exoplanet Research Centre. He is the founding director of the Center for the Origin and Prevalence of Life at ETH Zurich, established in 2022. He received the 2011 BBVA Foundation Frontiers of Knowledge Award in Basic Sciences and the 2017 Wolf Prize in Physics for his work on planet discoveries and orbital architecture.

Reader's Guide

Didier Queloz's significance lies in his pivotal role in the discovery of the first exoplanet orbiting a Sun-like star, 51 Pegasi b, in 1995. This breakthrough, achieved with Michel Mayor, fundamentally changed humanity's understanding of planetary systems and sparked the entire field of exoplanet research. For this, he shared the 2019 Nobel Prize in Physics. Beyond the initial discovery, Queloz made lasting contributions to the techniques of exoplanet detection. He developed methods to distinguish planetary signals from stellar activity, advanced radial velocity instrumentation through projects like ELODIE, CORALIE, and HARPS, and pioneered the combination of transit photometry and Doppler spectroscopy to measure planetary densities. His work on the Rossiter-McLaughlin effect revealed that many hot Jupiters have misaligned or retrograde orbits, providing new insights into planet formation. Later in his career, he focused on detecting Earth-like planets and searching for life, founding the Center for the Origin and Prevalence of Life at ETH Zurich. His legacy is that of a foundational figure in exoplanet science, whose technical innovations and discoveries opened a new window on the cosmos.

Did You Know?

• Queloz discovered 51 Pegasi b as part of his PhD at the University of Geneva, under the supervision of Michel Mayor.
• The discovery was made using the ELODIE spectrograph at the Haute-Provence Observatory.
• Queloz shared the 2019 Nobel Prize in Physics with Michel Mayor and Jim Peebles.
• He is the founding director of the Center for the Origin and Prevalence of Life at ETH Zurich, established in 2022.
• The Daily Telegraph reports Queloz as saying, 'Science inherited a lot from religions.'

The Discovery That Remade the Sky

In 1995, a young doctoral student at the University of Geneva, working under the supervision of Swiss astrophysicist Michel Mayor, announced a finding that would reshape humanity's view of the cosmos. Together, they identified a giant planet—later designated 51 Pegasi b—circling the star 51 Pegasi, a Sun-like main-sequence star. The world, classified as a Hot Jupiter, was never directly imaged; instead, its presence was inferred from tiny periodic shifts in the star's radial velocity, a gravitational signature produced by the orbiting body. Making that measurement possible was the ELODIE spectrograph, a newly developed instrument at the Haute-Provence Observatory, which let the team exploit the Doppler effect with a precision that had not previously been achievable. What began as a single detection quickly ignited what has since been called the exoplanet revolution, spawning an entirely new branch of astrophysics and fundamentally altering how scientists conceive of planetary systems beyond our own Solar System.

A Life Between Geneva, Cambridge, and Zurich

Born on 23 February 1966 in Switzerland, Queloz built his academic foundation at the University of Geneva, where he earned a master's degree in physics in 1990, a DEA in Astronomy and Astrophysics in 1992, and completed his doctoral work in 1995 under the supervision of Michel Mayor. His career then carried him across institutions and borders. He holds the Jacksonian Professorship of Natural Philosophy at the University of Cambridge, where he also serves as a fellow of Trinity College. In parallel, he maintains a professorship in physics at ETH Zurich. In 2022, he assumed the role of founding director of the Center for the Origin and Prevalence of Life at ETH Zurich, a position that places him at the intersection of planetary science and the broader question of whether life is widespread in the universe. In a remark reported by the Daily Telegraph, he observed that science inherited a great deal from religious traditions—a reflection that hints at the philosophical undercurrents running through his scientific work.

Building the Instruments That Found Worlds

Queloz's contributions extend far beyond a single discovery; he has been a driving force behind the instrumentation and analytical methods that made precise exoplanet detection possible. Early in his career, he recognized that stellar activity could masquerade as a planetary signal, and he published a landmark paper describing how to disentangle the two using proxy indicators and novel algorithms. Those methods have since become standard practice across the field of Doppler spectroscopy. He led the installation of CORALIE, an improved spectrograph on the Swiss 1.2-metre Leonhard Euler Telescope, which quickly began detecting planets on southern-hemisphere stars. In 2000, he assumed the role of project scientist for HARPS, a next-generation spectrograph on the ESO 3.6-metre telescope commissioned in 2003 that went on to become a reference instrument for precise radial velocity work. HARPS, combined with analysis software refined through years of experience with ELODIE and CORALIE, enabled the detection of smaller worlds in the Neptune and super-Earth range—planets that would later be confirmed in large numbers by the Kepler mission. For these instrumental and methodological advances, he received the 2011 BBVA Foundation Frontiers of Knowledge Award in Basic Sciences, shared with Mayor.

A Legacy Written in Distant Worlds

The 2019 Nobel Prize in Physics, shared with Michel Mayor and Jim Peebles, recognized Queloz's discovery as a contribution to humanity's understanding of the universe's evolution and Earth's place within it. The award capped a quarter-century of sustained scientific output during which his work focused on expanding the detection and measurement capabilities available to the exoplanet community. Over that span, he developed new astronomical equipment, devised novel observational approaches, and created detection algorithms that collectively led to the identification of hundreds of planets. His research also ventured into the architecture of planetary systems: in 2000 he achieved the first spectroscopic transit detection using the Rossiter-McLaughlin effect, and a decade later, through a collaboration with the Wide Angle Search for Planets consortium, he and his doctoral student demonstrated that a significant number of planets occupy misaligned or even retrograde orbits—a finding that provided fresh insight into their formation process. That body of work earned him the 2017 Wolf Prize in Physics. His 2022 appointment as founding director of the Center for the Origin and Prevalence of Life at ETH Zurich suggests the next chapter: moving from cataloguing worlds to asking whether they harbour life.