Michel Mayor

Michel Mayor
Born	Michel Gustave Édouard Mayor 12 1, 1942
Birthplace	Lausanne, Switzerland
Nationality	Swiss
Occupation	Astrophysicist, professor emeritus
Employer	University of Geneva
Known for	Discovery of 51 Pegasi b, the first exoplanet orbiting a Sun-like star
Education	University of Geneva (Ph.D., 1971)
Awards	Prix Jules Janssen (1998) Albert Einstein Medal (2004) Shaw Prize (2005) Kyoto Prize (2015) Wolf Prize in Physics (2017) Nobel Prize in Physics (2019)

Michel Gustave Édouard Mayor (born 12 January 1942) is a Swiss astrophysicist and professor emeritus at the University of Geneva's Department of Astronomy. In October 1995, together with his doctoral student Didier Queloz, Mayor announced the discovery of 51 Pegasi b, the first extrasolar planet found orbiting a main-sequence Sun-like star — a finding that fundamentally transformed humanity's understanding of planetary systems and its place in the cosmos. For this landmark achievement, Mayor and Queloz were awarded one half of the 2019 Nobel Prize in Physics, sharing the prize with James Peebles, who received the other half for theoretical discoveries in physical cosmology. Mayor formally retired in 2007 but has remained active as a researcher at the Geneva Observatory. Over the course of his career, he has received numerous international honors, including the Prix Jules Janssen (1998), the Albert Einstein Medal (2004), the Shaw Prize in Astronomy (2005), the Viktor Ambartsumian International Prize (2010), the Kyoto Prize in Basic Sciences (2015), and the Wolf Prize in Physics (2017). His work opened an entirely new field of astronomical research — the detection and characterization of exoplanets — that has since led to the identification of thousands of worlds beyond the Solar System.

Early Life

Michel Gustave Édouard Mayor was born on 12 January 1942 in Lausanne, Switzerland. In a 2019 interview with the Nobel Prize organization, Mayor recalled that his interest in science began at a young age, stating that he was "in fact interested in science from the age of 10 years." Growing up in the French-speaking part of Switzerland, Mayor developed an early curiosity about the natural world that would eventually lead him toward physics and astronomy.

Lausanne, situated on the shores of Lake Geneva and home to several prominent academic institutions, provided an environment conducive to intellectual development. Mayor's childhood interest in science evolved into a focused pursuit of physics during his secondary education, setting the stage for his university studies at nearby institutions in the Lake Geneva region. While specific details about his family background and upbringing remain limited in published sources, Mayor has spoken publicly about the formative role that early scientific curiosity played in shaping his career trajectory.

Education

Mayor began his higher education at the University of Lausanne, where he studied physics. He subsequently continued his graduate studies at the University of Geneva, where he pursued doctoral research in astrophysics. In 1971, Mayor completed his Ph.D. at the University of Geneva with a thesis entitled "The kinematical properties of stars in the solar vicinity: possible relation with the galactic spiral structure." This doctoral work focused on the study of stellar kinematics — the measurement and analysis of the motions of stars in the neighborhood of the Sun — and their potential connection to the large-scale spiral structure of the Milky Way galaxy. The thesis demonstrated Mayor's early expertise in precision measurements of stellar velocities, a skill set that would prove foundational to his later groundbreaking work in the detection of extrasolar planets through the radial velocity method.

Career

Early Research at the University of Geneva

Following the completion of his doctorate, Mayor joined the faculty of the University of Geneva's Department of Astronomy, which is associated with the Geneva Observatory (Observatoire de Genève) located in Sauverny, a suburb of Geneva. His early career was devoted to the study of stellar dynamics and the kinematics of stars in the Milky Way, building upon his doctoral research. This work involved developing and refining techniques for measuring the radial velocity of stars — the component of a star's velocity along the observer's line of sight — using spectroscopic instruments.

Throughout the 1970s and 1980s, Mayor and his colleagues at Geneva worked on improving the precision of radial velocity measurements. This was a technically demanding field that required increasingly sophisticated spectrographs and careful calibration methods. The Geneva group became one of the leading centers worldwide for radial velocity spectroscopy, and the expertise accumulated during these decades of instrument development and observational work laid the essential groundwork for the exoplanet discoveries that would follow.

Development of the ELODIE Spectrograph

A critical step toward the discovery of extrasolar planets was the development of the ELODIE spectrograph, a high-precision échelle spectrograph installed at the Haute-Provence Observatory in southeastern France. ELODIE was designed to achieve significantly higher precision in radial velocity measurements than had been previously possible with comparable instruments. The spectrograph was capable of detecting tiny Doppler shifts in the spectra of stars caused by the gravitational tug of orbiting companions — a technique that came to be known as the Doppler spectroscopy or radial velocity method of exoplanet detection.

The principle underlying this method is straightforward: if a planet orbits a star, the gravitational interaction causes the star to wobble slightly around the common center of mass of the star-planet system. This wobble produces periodic shifts in the wavelengths of the star's spectral lines as the star moves toward and away from the observer. By measuring these shifts with sufficient precision, astronomers can infer the presence of an unseen planetary companion, estimate its minimum mass, and determine its orbital period and eccentricity.

Discovery of 51 Pegasi b

In 1994, Mayor and his doctoral student Didier Queloz began a systematic survey of nearby Sun-like stars using the ELODIE spectrograph at the Haute-Provence Observatory. Their goal was to search for Jupiter-mass companions to solar-type stars. In the course of this survey, they detected a periodic radial velocity variation in the star 51 Pegasi, a G-type star located approximately 50 light-years from Earth in the constellation Pegasus.

The signal indicated the presence of a companion with a minimum mass roughly half that of Jupiter, orbiting the star with a period of just 4.23 days. This extraordinarily short orbital period implied that the planet was located extremely close to its host star — at a distance of only about 0.05 astronomical units (AU), or roughly one-eighth the distance between Mercury and the Sun. The discovery was startling because existing theories of planet formation, based on the architecture of our own Solar System, did not predict the existence of giant planets in such tight orbits. The object, designated 51 Pegasi b, came to be informally referred to as a "hot Jupiter" — a term that would subsequently be applied to an entire class of exoplanets sharing similar characteristics.

Mayor and Queloz announced their discovery on 6 October 1995 at a conference in Florence, Italy, and the results were published in the journal Nature on 23 November 1995 in a paper titled "A Jupiter-mass companion to a solar-type star." The discovery was swiftly confirmed by independent teams, including American astronomers Geoffrey Marcy and R. Paul Butler, and it electrified the scientific community. As the University of Geneva noted on the 30th anniversary of the discovery, the finding "changed humanity's place in our Galaxy" and "revolutioniz[ed] our understanding" of the universe.

While 51 Pegasi b was not the first extrasolar planet ever detected — earlier discoveries had been made around pulsars — it was the first exoplanet found orbiting a normal, hydrogen-burning, main-sequence star similar to the Sun. This distinction made it a milestone of exceptional significance, as it demonstrated that planetary systems could exist around ordinary stars and opened the prospect that planets might be common throughout the galaxy.

Continued Exoplanet Research

Following the discovery of 51 Pegasi b, Mayor continued to play a leading role in the rapidly expanding field of exoplanet research. He and his collaborators at Geneva, including Stéphane Udry and other members of the observatory's planet-hunting team, went on to discover numerous additional exoplanets using improved radial velocity techniques.

Among the notable subsequent discoveries was work on the planetary system around the star Gliese 581, a red dwarf located about 20 light-years from Earth. In 2009, Mayor was a co-author on a study reporting the detection of Gliese 581 e, which at the time was identified as one of the least massive exoplanets known, with a minimum mass of approximately 1.9 Earth masses. The Gliese 581 system attracted significant scientific and public attention because several of its planets were located near or within the star's habitable zone — the range of orbital distances where liquid water could potentially exist on a planet's surface.

Mayor was also instrumental in the development and use of the HARPS (High Accuracy Radial velocity Planet Searcher) spectrograph, installed at the European Southern Observatory's 3.6-metre telescope at La Silla Observatory in Chile. HARPS represented a significant advance in radial velocity precision over ELODIE, achieving measurement accuracies on the order of one meter per second. This increased precision enabled the detection of smaller, lower-mass planets, including "super-Earths" and potentially rocky worlds.

Mentorship and the Geneva Exoplanet Group

Mayor played a significant role as a mentor and research supervisor at the University of Geneva. Didier Queloz, who co-discovered 51 Pegasi b while working as Mayor's doctoral student, went on to become one of the most prominent exoplanet researchers in the world and shared the 2019 Nobel Prize with Mayor. The research group that Mayor helped build at the Geneva Observatory became one of the foremost centers for exoplanet detection and characterization globally, contributing to the discovery of hundreds of extrasolar planets over the following decades.

A New York Times profile described Mayor's contributions to the field and his role in transforming the study of extrasolar planets from a speculative endeavor into a mainstream branch of astrophysics.

Retirement and Continued Activity

Mayor formally retired from the University of Geneva in 2007 but retained the title of professor emeritus and has continued to be active as a researcher at the Geneva Observatory. In the years following his retirement, he has continued to participate in scientific conferences, public lectures, and outreach activities. In 2025, he delivered a lecture at Academia Sinica in Taiwan as part of the TAIWAN BRIDGES lecture series, speaking about exoplanets and the question of extraterrestrial life.

Mayor has also participated in public lectures at institutions such as the University of California, San Diego, where he spoke in March 2016 as part of the annual Kyoto Prize Symposium.

Personal Life

Mayor has spoken publicly about his views on the implications of exoplanet discoveries for humanity. In interviews, he has expressed skepticism about the feasibility of human migration to extrasolar planets, noting that such worlds are "much, much too far away" and that reaching them would take "hundreds of millions of days using the means we have available today." At the same time, he has indicated that the discovery of exoplanets makes the search for extraterrestrial communications a more practical consideration than previously thought.

Mayor resides in Switzerland and has maintained his association with the University of Geneva and its observatory throughout his career and into his retirement years. The minor planet 125076 Mayor is named in his honor.

Recognition

Mayor has received numerous awards and honors throughout his career in recognition of his contributions to astrophysics and planetary science.

In 1998, he was awarded the Prix Jules Janssen by the Société astronomique de France, one of the highest distinctions in French astronomy. In 2004, he received the Albert Einstein Medal from the Albert Einstein Society in Bern, Switzerland. In 2005, Mayor shared the Shaw Prize in Astronomy, one of the most prestigious awards in the sciences, sometimes referred to as the "Nobel of the East."

In 2010, Mayor was awarded the Viktor Ambartsumian International Prize, an international award recognizing outstanding contributions to astrophysics and related sciences.

In 2015, Mayor received the Kyoto Prize in Basic Sciences, awarded by the Inamori Foundation in Japan. The Kyoto Prize is one of the most significant international awards for lifetime achievement in the sciences, arts, and philosophy.

In 2015, Mayor also received a Gold Medal from the Royal Astronomical Society.

In 2017, Mayor shared the Wolf Prize in Physics with Didier Queloz, further cementing recognition of their joint achievement.

The culmination of these honors came on 8 October 2019, when the Royal Swedish Academy of Sciences announced that Mayor and Queloz would share one half of the 2019 Nobel Prize in Physics "for the discovery of an exoplanet orbiting a solar-type star." The other half was awarded to James Peebles "for theoretical discoveries in physical cosmology." The Nobel citation recognized that these laureates had made "contributions to our understanding of the evolution of the universe and Earth's place in the cosmos."

Legacy

The discovery of 51 Pegasi b by Mayor and Queloz in 1995 is recognized as one of the transformative moments in the history of astronomy. Prior to their announcement, the existence of planets outside the Solar System had been a matter of theoretical speculation; after it, the study of exoplanets became one of the most active and productive areas of astrophysical research. As the University of Geneva stated on the 30th anniversary of the discovery, the finding from the Geneva Observatory "changed humanity's place in our Galaxy."

The discovery had far-reaching scientific consequences. It demonstrated that giant planets could exist in orbital configurations radically different from those in the Solar System, challenging prevailing models of planet formation and migration. The existence of "hot Jupiters" — gas giants orbiting their host stars at very close distances — had not been predicted by theory and prompted a major reassessment of how planetary systems form and evolve.

Moreover, Mayor's work catalyzed a global effort to detect and characterize exoplanets that has continued to expand in the decades since. The radial velocity technique pioneered at Geneva has been complemented by other detection methods, including the transit photometry method employed by space missions such as Kepler and TESS. As of the 30th anniversary of the discovery in 2025, thousands of exoplanets have been confirmed, revealing an extraordinary diversity of planetary systems.

Mayor's impact extends beyond the specific discovery of 51 Pegasi b. Through his development of precision spectrographic instruments, his leadership of the Geneva planet-hunting program, and his mentorship of younger researchers including Queloz, he helped establish the institutional and technical foundations of modern exoplanet science. The ELODIE and HARPS spectrographs developed under his direction set standards for precision radial velocity measurements that influenced the design of subsequent instruments worldwide.

The naming of minor planet 125076 Mayor in his honor serves as a lasting astronomical tribute. Mayor's public engagement in his later years, including lectures on the possibility of extraterrestrial life and the implications of exoplanet discoveries, has helped bring the significance of this research to broader audiences around the world.