Didier Queloz is a professor of physics at the University of Cambridge’s Cavendish Laboratory and professor of astronomy at the University of Geneva (part time). He is one of the originators of the “exoplanet revolution” in astrophysics. In 1995, as part of his PhD, he and his supervisor announced the first discovery of a giant planet orbiting another star, outside the solar system¹. The planet was detected by the measurement of small periodic changes in stellar radial velocity produced by the orbiting planet. Detecting this small variability using the Doppler effect was possible thanks to the development of a new type of spectrograph combining stability, high resolution and a creative approach to measure precise stellar radial velocity². For his work he was awarded, with Michel Mayor, the 2011 BBVA Foundation Frontiers of Knowledge Award of Basic Sciences for “developing new astronomical instruments and experimental techniques that led to the first observation of planets outside the Solar System.”

This seminal discovery spawned a revolution in astronomy and kickstarted the research field of exoplanet systems. Over the next 25 years, Didier Queloz’s main scientific contributions have essentially focused on expanding the 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 our solar system. In the course of his career, he has developed new astronomical equipment, novel observational approaches and detection algorithms. He has participated in and conducted programs leading to the detection of hundreds of planets, include breakthrough results.

Early in his career, he identified stellar activity as a potential limitation for planet detection. He published a reference paper⁶ 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 of precise Doppler spectroscopy data. His teamⁱ and his Geneva colleaguesⁱⁱ established standards to optimise measurements of stellar radial velocity that are still in use today.⁵

Shortly after the start of the ELODIE planet survey at the Haute-Provence Observatory (OHP), he led the installation of an improved version (CORALIE), on the Swiss Euler telescope in Chile. Very quickly this new facility started to detect exoplanets on stars visible in the southern hemisphere.⁴ In 2000 he took responsibility, as project scientist, for the development of HARPS⁷, a new type of spectrograph for the European Southern Observatory (ESO) 3.6m telescope. This instrument, commissioned in 2003, was to set a new standard in the business of precise Doppler spectroscopy⁸. HARPS’ performance, allied with the development of new analysis software inherited from data gathered by 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^10,11 before NASA’s Kepler space telescope would massively detect them and establish their statistical occurrence.

After the announcement of the detection of the first transiting planet (in 1999), Didier Queloz’s research interests broadened, with the objective to combine capabilities offered by transiting planets and follow-up Doppler spectroscopy measurements. In 2000 he achieved the first spectroscopic transit detection of an exoplanet using the so-called Rossiter-McLaughlin effect.³ 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 collaboration with the Wide Angle Search for Planets (WASP) consortium in the UK. With his PhD studentⁱⁱⁱ he demonstrated that a significant number of planets were surprisingly misaligned or on retrograde orbits, providing new insights about their formation process. 2017 he received the 2017 Wolf Prize in Physics for his “seminal work on revealing an incredible diversity of exoplanets and his contribution to the discovery of more than 250 additional exoplanets, including several multi-planetary systems and measurement of the first Rossiter-McLaughlin effect for a transiting planet, which allowed the measurement of the projected angle between the stellar spin axis and the planets orbital axis […]”

The special geometry of transiting planets, combined with precise Doppler spectroscopic observations, allows us to measure the mass and radius of planets and to compute their bulk densities in order to gain insights about their physical structure. In 2003, Didier Queloz − recently appointed to a faculty position − with his teamiv pioneered and established the combination of these techniques by first measuring bulk density of OGLE transiting planets9. They also looked for transit opportunities on known radial velocity planets and they found the first transiting Neptune-sized planet (GJ436b).¹³ In the course of this program and in collaboration with his colleague Shay Zucker from Tel-Aviv University, he developed the mathematical foundation to compute residual noise they encountered during the analysis of transit they were trying to model. They established a statistical metric to evaluate “red noise.”¹² Today this concept is widely used in the field to estimate systematics in light-curves and transit modeling.

In 2007 Didier Queloz became an associate professor. Over the next 5 years following his appointment, his research program − based on a combination of spectroscopy and transit detection − intensified. He took the lead in the spectroscopic follow-up effort of the WASP consortium and the Eureopean Space Administration’s Corot space mission.^v The combination of WASP and Corot data with follow-up observations using Euler-Cam (a CCD imager he developed), CORALIE, HARPS and other main ESO facilities was amazingly successful. It led to more than 100 publications, some of them breakthroughs providing us with new insights on formation and nature of hot Jupiter-type planets. Further, in the same period, the detection of COROT-7b − combined with intensive follow-up work − established the first detection of a planet with a bulk density similar to a rocky planet.¹⁴

All the follow-up expertise he developed naturally extended to the Kepler mission era, with the HARPS-N consortium confirming the Earth-like bulk density of Kepler10.¹⁶ In ground-based transit programs, Didier Queloz was deeply involved in the design and installation of a new generation survey telescope: the Next Generation Transit Survey (NGTS) observatory. His role was decisive during system tests in Europe and in establishing the facility at Paranal, Chile.²⁰

At the time Didier Queloz moved to Cambridge, he essentially focused on setting up comprehensive research activities directed to the detection of Earth-like planets and life in the universe and to the further development of the exoplanet community in the UK. When he left Switzerland, he was co-directing a major national initiative^vi which eventually got funded. At Cambridge, with the help of his colleagues at the Institute of Astronomy (IoA) and the Department of Applied Mathematics and Theoretical Physics (DAMTP), he established the Cambridge Exoplanet Research Centre^vii to stimulate joint coordinated efforts and collaboration between departments. In the UK he organized the first “exoplanet comunity meeting” and installed the idea of a regular yearly community workshop. In the European context, he is leading at Geneva (through his joint professorial appointment) the development of the ground segment of the CHaracterizing ExOPlanet Satellite (CHEOPS)^viii space mission and he chairs the science team.

His most recent research highlights are related to the search for transing Earth-like planets near low-mass stars and for extraterrestrial life. This program, carried out in collaboration with Michael Gillon of the University of Liège, is the origin of the detection of Trappist-1¹⁸, a planetary system of potential interest to further searches for atmospheres and signs of life. Another successful avenue of research is the characterization of the rocky surface or atmosphere of hot small planets, including the work on 55 Cnc.¹⁷ The recent extension of this program towards extraterrestrial life is being carried out in the context of an international research initiative supported by the Simons Foundation. One major result of this collaboration is the definition – combining chemistry and astrophysical constraints – of minimum conditions for the origins of RNA precursors on exoplanets (“abiogenesis zone”).¹⁹

Discoveries of exoplanets attract a lot of attention from the public and the media. In parallel with his research and teaching activities, Didier Queloz has been involved in numerous documentary films, has written articles and has done TV and radio interviews to share his excitement, explain his findings and promote a general interest in science.

Publications

1. Michel Mayor and Didier Queloz. “A Jupiter-mass companion to a solar-type star.” In: Nature 378, 6555 (Nov. 1995), pp. 355–359. doi: 10.1038/ 378355a0.
2. A. Baranne, D. Queloz, M. Mayor, G. Adrianzyk, G. Knispel, D. Kohler, D. Lacroix, J. -P. Meunier, G. Rimbaud, and A. Vin. “ELODIE: A spectrograph for accurate radial velocity measurements.” In: Astronomy & Astrophysics 119 (Oct. 1996), pp. 373–390.
3. D. Queloz, A. Eggenberger, M. Mayor, C. Perrier, J. L. Beuzit, D. Naef, J. P. Sivan, and S. Udry. “Detection of a spectroscopic transit by the planet orbiting the star HD209458.” In: Astronomy & Astrophysics 359 (July 2000), pp. L13– L17. arXiv: astro-ph/0006213 [astro-ph].
4. D. Queloz, M. Mayor, L. Weber, A. Blécha, M. Burnet, B. Confino, D. Naef, F. Pepe, N. Santos, and S. Udry. “The CORALIE survey for southern extra-solar planets. I. A planet orbiting the star Gliese 86.” In: Astronomy & Astrophysics 354 (Feb. 2000), pp. 99–102.
5. F. Bouchy, F. Pepe, and D. Queloz. “Fundamental photon noise limit to radial velocity measurements.” In: Astronomy & Astrophysics 374 (Aug. 2001), pp. 733– 739. doi: 10.1051/0004-6361:20010730.
6. D. Queloz, G. W. Henry, J. P. Sivan, S. L. Baliunas, J. L. Beuzit, R. A. Donahue,
   M. Mayor, D. Naef, C. Perrier, and S. Udry. “No planet for HD 166435.” In: Astronomy & Astrophysics 379 (Nov. 2001), pp. 279–287. doi: 10.1051/0004-6361: 20011308. arXiv: astro-ph/0109491 [astro-ph].
7. D. Queloz, M. Mayor, S. Udry, M. Burnet, F. Carrier, A. Eggenberger, D. Naef, N. Santos, F. Pepe, G. Rupprecht, G. Avila, F. Baeza, W. Benz, J. L. Bertaux, F. Bouchy, C. Cavadore, B. Delabre, W. Eckert, J. Fischer, M. Fleury, A. Gilliotte, D. Goyak, J. C. Guzman, D. Kohler, D. Lacroix, J. L. Lizon, D. Megevand, J. -P. Sivan, D. Sosnowska, and U. Weilenmann. “From CORALIE to HARPS. The way towards 1 m s−1 precision Doppler measurements.” In: The Messenger 105 (Sept. 2001), pp. 1–7.
8. M. Mayor, F. Pepe, D. Queloz, F. Bouchy, G. Rupprecht, G. Lo Curto, G. Avila,
   W. Benz, J. -L. Bertaux, X. Bonfils, Th. Dall, H. Dekker, B. Delabre, W. Eckert,
   M. Fleury, A. Gilliotte, D. Gojak, J. C. Guzman, D. Kohler, J. -L. Lizon, A. Longinotti, C. Lovis, D. Megevand, L. Pasquini, J. Reyes, J. -P. Sivan, D. Sosnowska, R. Soto, S. Udry, A. van Kesteren, L. Weber, and U. Weilenmann. “Setting New Standards with HARPS.” In: The Messenger 114 (Dec. 2003), pp. 20–24.
9. F. Pont, F. Bouchy, D. Queloz, N. C. Santos, C. Melo, M. Mayor, and S. Udry. “The “missing link:” A 4-day period transiting exoplanet around
   OGLE-TR-111.” In: Astronomy & Astrophysics 426 (Oct. 2004), pp. L15–L18. doi: 10.1051/ 0004-6361:200400066. arXiv: astro-ph/0408499 [astro-ph].
10. N. C. Santos, F. Bouchy, M. Mayor, F. Pepe, D. Queloz, S. Udry, C. Lovis, M. Bazot, W. Benz, J. -L. Bertaux, G. Lo Curto, X. Delfosse, C. Mordasini, D. Naef,
    J. -P. Sivan, and S. Vauclair. “The HARPS survey for southern extra-solar planets. II. A 14 Earth-masses exoplanet around µ Arae.” In: Astronomy & Astrophysics 426 (Oct. 2004), pp. L19–L23. doi: 10.1051/0004-6361: 200400076. arXiv: astro-ph/0408471 [astro-ph].
11. Christophe Lovis, Michel Mayor, Francesco Pepe, Yann Alibert, Willy Benz, Francois Bouchy, Alexandre C. M. Correia, Jacques Laskar, Christoph Mordasini, Didier Queloz, Nuno C. Santos, Stéphane Udry, Jean-Loup Bertaux, and Jean-Pierre Sivan. “An extrasolar planetary system with three Neptune-mass planets.” In: Nature 441, 7091 (May 2006), pp. 305– 309. doi: 10.1038/ nature04828. arXiv: astro-ph/0703024 [astro-ph].
12. Frédéric Pont, Shay Zucker, and Didier Queloz. “The effect of red noise on planetary transit detection.” In: Monthly Notices of the Royal Astronomical Society 373, 1 (Nov. 2006), pp. 231– 242. doi: 10.1111/j.1365-2966.2006.11012.x. arXiv: astro-ph/0608597 [astro-ph].
13. M. Gillon, F. Pont, B. -O. Demory, F. Mallmann, M. Mayor, T. Mazeh, D. Queloz,
    A. Shporer, S. Udry, and C. Vuissoz. “Detection of transits of the nearby hot Neptune GJ 436 b.” In: Astronomy & Astrophysics 472, 2 (Sept. 2007), pp. L13– L16. doi: 10.1051/0004-6361:20077799. arXiv: 0705.2219 [astro-ph].
14. D. Queloz, F. Bouchy, C. Moutou, A. Hatzes, G. Hébrard, R. Alonso, M. Auvergne, A. Baglin, M. Barbieri, P. Barge, W. Benz, P. Bordé, H. J. Deeg, M. Deleuil, R. Dvorak, A. Erikson, S. Ferraz Mello, M. Fridlund, D. Gandolfi, M. Gillon, E. Guenther, T. Guillot, L. Jorda, M. Hartmann, H. Lammer, A. Léger, A. Llebaria, C. Lovis, P. Magain, M. Mayor, T. Mazeh, M. Ollivier, M. Pätzold, F. Pepe, H. Rauer, D. Rouan, J. Schneider, D. Segransan, S. Udry, and G. Wuchterl. “The CoRoT-7 planetary system: two orbiting super-Earths.” In: Astronomy & Astrophysics 506, 1 (Oct. 2009), pp. 303–319. doi: 10.1051/0004-6361/200913096.
15. A. H. M. J. Triaud, A. Collier Cameron, D. Queloz, D. R. Anderson, M. Gillon, L. Hebb, C. Hellier, B. Loeillet, P. F. L. Maxted, M. Mayor, F. Pepe, D. Pollacco, D. Ségransan, B. Smalley, S. Udry, R. G. West, and P. J. Wheatley. “Spin-orbit angle measurements for six southern transiting planets. New insights into the dynamical origins of hot Jupiters.” In: Astronomy & Astrophysics 524, A25 (Dec. 2010), A25. doi: 10.1051/0004-6361/201014525. arXiv: 1008.2353 [astro-ph.EP].
16. Francesco Pepe, Andrew Collier Cameron, David W. Latham, Emilio Molinari, Stéphane Udry, Aldo S. Bonomo, Lars A. Buchhave, David Charbonneau, Rosario Cosentino, Courtney D. Dressing, Xavier Dumusque, Pedro Figueira, Aldo F. M. Fiorenzano, Sara Gettel, Avet Harutyunyan, Raphaëlle D. Haywood, Keith Horne, Mercedes Lopez-Morales, Christophe Lovis, Luca Malavolta, Michel Mayor, Giusi Micela, Fatemeh Motalebi, Valerio Nascimbeni, David Phillips, Giampaolo Piotto, Don Pollacco, Didier Queloz, Ken Rice, Dimitar Sasselov, Damien Ségransan, Alessandro Sozzetti, Andrew Szentgyorgyi, and Christopher A. Watson. “An Earth-sized planet with an Earth-like density.” In: Nature 503, 7476 (Nov. 2013), pp. 377–380. doi: 10.1038/nature12768. arXiv: 1310.7987 [astro-ph.EP].
17. Brice-Olivier Demory, Michael Gillon, Nikku Madhusudhan, and Didier Queloz. “Variability in the super-Earth 55 Cnc e.” In: Monthly Notices of the Royal Astronomical Society 455, 2 (Jan. 2016), pp. 2018–2027. doi: 10.1093/mnras/ stv2239. arXiv: 1505.00269 [astro-ph.EP].
18. Michaël Gillon, Emmanuël Jehin, Susan M. Lederer, Laetitia Delrez, Julien de Wit, Artem Burdanov, Valérie Van Grootel, Adam J. Burgasser, Amaury H. M. J. Triaud, Cyrielle Opitom, Brice-Olivier Demory, Devendra K. Sahu, Daniella Bardalez Gagliuffi, Pierre Magain, and Didier Queloz. “Temperate Earth-sized planets transiting a nearby ultracool dwarf star.” In: Nature 533, 7602 (May 2016), pp. 221–224. doi: 10.1038/nature17448. arXiv: 1605.07211 [astro-ph.EP].
19. Paul B. Rimmer, Jianfeng Xu, Samantha J. Thompson, Ed Gillen, John D. Sutherland, and Didier Queloz. “The origin of RNA precursors on exoplanets.” In: Science Advances 4, 8 (Aug. 2018), eaar3302. doi: 10. 1126/sciadv.aar3302. arXiv: 1808.02718 [astro-ph.EP].
20. Peter J. Wheatley, Richard G. West, Michael R. Goad, James S. Jenkins, Don L. Pollacco, Didier Queloz, Heike Rauer, Stéphane Udry, Christopher A. Watson, Bruno Chazelas, Philipp Eigmüller, Gregory Lambert, Ludovic Genolet, James McCormac, Simon Walker, David J. Armstrong, Daniel Bayliss, Joao Bento, Francois Bouchy, Matthew R. Burleigh, Juan Cabrera, Sarah L. Casewell, Alexander Chaushev, Paul Chote, Szilárd Csizmadia, Anders Erikson, Francesca Faedi, Emma Foxell, Boris T. Gänsicke, Edward Gillen, Andrew Grange, Maximilian N. Günther, Simon T. Hodgkin, James Jackman, Andrés Jordán, Tom Louden, Lionel Metrailler, Maximiliano Moyano, Louise D. Nielsen, Hugh P. Osborn, Katja Poppenhaeger, Roberto Raddi, Liam Raynard, Alexis M. S. Smith, Maritza Soto, and Ruth Titz-Weider. “The Next Generation Transit Survey (NGTS).” In: Monthly Notices of the Royal Astronomical Society 475, 4 (Apr. 2018), pp. 4476–4493. doi: 10.1093/mnras/stx2836. arXiv: 1710.11100 [astro-ph.EP].

i. Francois Bouchy (postdoc)
ii. Francesco Pepe (HARPS project manager)
iii. Amaury Triaud (PhD student)
iv. Francois Bouchy, Michael Gillon, Frédric Pont (Postdocs)
v. COROT CNES webpage
vi. PlanetS webpage: http://nccr-planets.ch/
vii. Cambridge Exoplanet Centre
viii. CHEOPS webpage: http://exoplanets.phy.cam.ac.uk/

This autobiography/biography was written at the time of the award and later published in the book series Les Prix Nobel/ Nobel Lectures/The Nobel Prizes. The information is sometimes updated with an addendum submitted by the Laureate.