The quest to understand our place in the universe took a giant leap forward in the 1990s with the groundbreaking discovery of the first planet orbiting a sun-like star. That discovery, and the decades of work that followed, is largely credited to the Swiss astrophysicist Didier Queloz, who shared the 2019 Nobel Prize in Physics for his contributions to the field of exoplanet research. Queloz’s work has fundamentally reshaped our understanding of planetary systems and fueled the search for life beyond Earth.
Born in Geneva in 1966, Queloz demonstrated an early passion for learning, particularly as he progressed through the Swiss cantonal and federal school system. This innate curiosity led him to pursue studies in physics, a discipline he would dedicate his career to. In 1990, he began his doctoral research in astrophysics with Michel Mayor at the Observatoire de Haute-Provence in France. Their focus was on developing the technology needed to detect planets orbiting other stars – exoplanets – by precisely measuring the wobble in a star’s movement caused by the gravitational pull of an orbiting planet, a technique known as radial velocity.
The team secured telescope time in 1993 to observe 142 stars similar to our sun. It was in 1994 that Queloz began observing a star, 51 Pegasi, located approximately 50.9 light-years from Earth, and noticed periodic variations in its light. These variations, occurring every 4.2 days, were initially perplexing. As Queloz recounted, Mayor initially responded that such a short orbital period wasn’t predicted by existing theory. Although, after rigorous verification, they confirmed the existence of an object – a planet – orbiting 51 Pegasi with a mass about half that of Jupiter, completing an orbit in just 4.2 days. This remarkable finding was published in the journal Nature in 1995, marking the beginning of what became known as the “revolution of exoplanets.”
The discovery of 51 Pegasi b challenged existing models of planetary formation, which largely predicted gas giants like Jupiter to reside far from their stars. This “hot Jupiter” – a massive planet orbiting incredibly close to its star – forced scientists to rethink their understanding of how planetary systems evolve. The European Southern Observatory (ESO) celebrated the Nobel Prize awarded to Mayor and Queloz, highlighting their pioneering work and the crucial role of ESO’s facilities, such as the HARPS spectrograph at the La Silla Observatory and ESPRESSO on the Very Large Telescope, in the ongoing search for exoplanets.
From Geneva to Cambridge and Beyond
Queloz’s career has been marked by continued dedication to exoplanet research and a growing list of accolades. He is a member of the Royal Society and held the prestigious Jacksonian professorship of Natural Philosophy at the University of Cambridge. Since September 2021, he has been a professor of physics at ETH Zürich. He is likewise a member of Trinity College at Cambridge.
Beyond the initial discovery of 51 Pegasi b, Queloz has been instrumental in the detection of hundreds of other planets and the measurement of their physical characteristics. His contributions include the discovery of Gliese 436 b, the first Neptune-sized planet found to transit (pass in front of) its star, and precise measurements of the mass of COROT-7b, confirming the existence of planets with densities similar to rocky planets. These discoveries have broadened our understanding of the diversity of exoplanets and increased the likelihood of finding potentially habitable worlds.
The Ongoing Search for Habitable Worlds
The impact of Queloz’s work extends far beyond the scientific community. The discovery of exoplanets has captured the public imagination and fueled the search for extraterrestrial life. The possibility of finding planets capable of supporting life – planets with liquid water, a stable atmosphere, and a suitable temperature – is a driving force behind ongoing exoplanet research. The field continues to evolve with new technologies and missions, such as the James Webb Space Telescope, which are providing unprecedented insights into the atmospheres of exoplanets and their potential for habitability. Recent discussions at the Mucem highlight the ongoing exploration of these “new worlds in the cosmos.”
Queloz’s legacy is not just in the planets he has discovered, but in the foundation he has laid for future generations of astronomers, and astrobiologists. His work has transformed exoplanet research from a theoretical pursuit into a vibrant and rapidly evolving field. The search for exoplanets, and the potential for life beyond Earth, remains one of the most compelling scientific endeavors of our time.
The next major milestone in exoplanet research will be the continued analysis of data from the James Webb Space Telescope, which is expected to provide more detailed information about the atmospheres of potentially habitable exoplanets. Scientists are eagerly awaiting these results, which could offer clues about the presence of biomarkers – indicators of life – in the atmospheres of distant worlds.
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