Didier Queloz

Didier Patrick Queloz (born 23 February 1966) is a Swiss astronomer.

He is the Jacksonian Professor of Natural Philosophy at the University of Cambridge, where he is also a fellow of Trinity College, Cambridge, as well as a professor at the University of Geneva.

Queloz was born in Switzerland, on 23 February 1966.

Queloz studied at the University of Geneva where he subsequently obtained a MSc degree in physics in 1990, a DEA in Astronomy and Astrophysics in 1992, and a PhD degree in 1995 with Swiss astrophysicist Michel Mayor as his doctoral advisor.

In the area of religion The Daily Telegraph reports him as saying, "although not a believer himself, “Science inherited a lot from religions”".

Didier Queloz is at the origin of the “exoplanet revolution” in astrophysics when as part of his PhD at the University of Geneva, with his supervisor, they discovered the first exoplanet around a main sequence star.

Together with Michel Mayor in 1995, he discovered 51 Pegasi b, the first extrasolar planet orbiting a Sun-like star, 51 Pegasi.

In 1995 with Michel Mayor announced a giant planet orbiting the star 51 Pegasi; the planet was identified as 51 Pegasi b and determined to be of a Hot Jupiter.

The planet was detected by the measurement of small periodic changes in stellar radial velocity produced by the orbiting planet.

Detecting this small variability by the Doppler effect had been possible thanks to the development of a new type of spectrograph, ELODIE, installed at the Haute-Provence Observatory, combined creative approach to measuring precise stellar radial velocity.

After the announcement of the detection of the first transiting planet (in 1999), Didier Queloz's research interest got broader with the objective to combine capabilities offered by transiting planets and follow-up Doppler spectroscopy measurements.

In 2000, he took the responsibility, as a project scientist, in the development of HARPS, a new type of spectrograph for the ESO 3.6m telescope.

In 2000 he achieved the first spectroscopic transit detection of an exoplanet using the so-called Rossiter-McLaughlin effect.

This type of measurement essentially tells us about the projected angle between the stellar angular momentum vector and the planet orbital angular momentum vector.

The pinnacle of this program would be reached 10 years later, after he led a significant upgrade of CORALIE, and established a collaboration with the Wide Angle Search for Planets (WASP) consortium in the UK.

With his Ph.D. student they demonstrated a significant number of the planets were surprisingly misaligned or in a retrograde orbit, providing a new insight about their formation process.

This instrument commissioned in 2003 was about to become a reference in the business of precise Doppler spectroscopy.

HARPS performances, allied with the development of a new analysis software inherited from all past experiences gathered with ELODIE and CORALIE, would considerably improve the precision of the Doppler technique.

Eventually, it would deliver spectacular detections of smaller exoplanets in the realm of Neptune, super-Earth systems before Kepler would massively detect them and establish their statistic occurrence.

In 2003 Didier Queloz, recently appointed at a faculty position, with his research team pioneered and established the combination of these techniques by first measuring bulk density of OGLE transiting planets.

They also looked for transit opportunities on known radial velocity planets and they found the first transiting Neptune-size planet Gliese 436 b.

In the course of this program and a collaboration with his Colleague S. Zucker from Tel-Aviv University, they developed the mathematical foundation to compute residual noise they encountered during the analysis of transit they were trying to model.

They established statistical metric to address pink noise in the data.

Today this concept is widely used in the field to estimate systematics in light-curves and transit modelling.

Queloz received the 2011 BBVA Foundation Frontiers of Knowledge Award of Basic Sciences (co-winner with Mayor) for developing new astronomical instruments and experimental techniques that led to the first observation of planets outside the solar system.

Shortly after the start of the ELODIE planet survey at OHP, he led the installation of an improved version (CORALIE), on the Swiss 1.2-metre Leonhard Euler Telescope.

Very quickly this new facility started to detect exoplanets on stars visible in the southern hemisphere.

In 2017 he received the Wolf Prize in Physics 2017 for that work and all the planet discoveries he had made.

The special geometry of transiting planets combined with precise Doppler spectroscopic observations allow us to measure the mass and radius of planets and to compute their bulk densities to get insights about their physical structure.

For this discovery, he shared the 2019 Nobel Prize in Physics with Mayor and Jim Peebles.

In 2021, he was announced as the founding director of the Center for the Origin and Prevalence of Life at ETH Zurich.

For this achievement, they were awarded half of the 2019 Nobel Prize in Physics "for the discovery of an exoplanet orbiting a solar-type star" resulting in “contributions to our understanding of the evolution of the universe and Earth’s place in the cosmos.”

This seminal discovery has spawned a revolution in astronomy and kickstarted the research field of exoplanets.

Over the next 25 years, Didier Queloz's main scientific contributions have essentially been focused to expand our detection and measurement capabilities of these systems to retrieve information on their physical structure.

The goal is to better understand their formation and evolution by comparison with the Solar System.

In the course of his career, he developed new astronomical equipment, novel observational approaches, and detection algorithms.

He participated and conducted programs leading to the detection of hundred planets, including breakthrough results.

Early in his career, he identified stellar activity as a potential limitation for planet detection.

He published a reference paper describing how to disentangle stellar activity from a planetary signal using proxies, including new algorithms that have become standard practice in all planet publications based on precise Doppler spectroscopy data.

With this work he set the foundation to optimize measurements of stellar radial velocity that is still in use today.