“My world is the world of discovery of planet,” Nobel laureate and physics professor at ETH Zurich Didier Queloz said at the Shanghai Master Forum on Science on November 17, in a lecture on the exoplanet revolution and cosmic life.
During his doctoral studies, Queloz—together with his advisor Michel Mayor—made a breakthrough in 1995: they discovered the first planet orbiting a star outside the solar system. The finding proved the universe is far bigger than people had imagined, sparked a revolution in astronomy, and laid the foundation for modern exoplanet research.
Then, does life exist elsewhere in the universe? To answer this profound question, Queloz has delved into research for years. He was quick to clarify, though, that his exploration is never about leaving—it’s about learning to live peacefully on our shared home, Earth.
From a “Crazy” Signal to a Cosmic Revolution
In the autumn of 1995, doctoral student Queloz, working under the supervision of Michel Mayor, detected an unusual signal in data from a French telescope—a subtle, periodic wobble in the light from the star 51 Pegasi. This anomaly, attributed to the gravitational pull of an unseen companion, led to a groundbreaking discovery: the first confirmed exoplanet orbiting a Sun-like star beyond our solar system—a finding that would fundamentally reshape our understanding of the cosmos.
This breakthrough, which earned Queloz and Mayor the Nobel Prize in Physics in 2019, proved that our solar system was not unique. It brought us closer to answering an age-old question: Are we alone in the universe?
At the time, the existence of planets orbiting Sun-like stars remained purely theoretical. Queloz was not actively searching for exoplanets but was instead measuring variations in stellar radial velocities. Employing the radial velocity method, he identified a subtle, periodic Doppler Shift in the spectrum of 51 Pegasi.
“If you study the star’s light in great detail, you see a slight change in colour (wavelength). It’s called the Doppler Shift, and we use that to find your planet,” Queloz explained.
The signal indicated a planet with an astonishingly short orbital period of just over four days—a “Hot Jupiter” radically different from anything in our own solar system. After exhaustive checks, the wobble persisted. He faxed his supervisor, Mayor, to say he thought he’d found a planet.
A New Window on the Universe
The planet, named 51 Pegasi b, proved that planetary systems are common. Queloz said that it had been a huge shift in perception. “That would be a fantastic signal that life elsewhere follows the same pathway.”
This discovery shattered the long-held notion of our solar system’s special status. It demonstrated that planet formation was a robust and universal process, directly challenging existing planetary formation theories and spurring new hypotheses like planetary migration.
In the three decades since, astronomers have confirmed over 6,000 exoplanets, revealing an astonishing diversity far beyond our solar system’s census—from “super-Earths” and “mini-Neptunes” to “ultra-hot Jupiters” with temperatures high enough to vaporize iron.
Intelligent Life Out There?
This explosion in known worlds has transformed the search for life from philosophical speculation into a tangible, data-driven science.
By analyzing starlight that filters through a distant planet's atmosphere, scientists can detect the chemical fingerprints of molecules like hydrogen, sodium, iron, and even water vapor. Queloz highlighted detections of carbon dioxide and methane in some exoplanet atmospheres. While not direct proof of life, these gases point to potentially habitable chemical environments.
“Are we alone in the universe? What other entity might exist, and why did life arise on Earth?” Queloz said, adding that “absence of evidence is not evidence of absence.”
Queloz’s work at the University of Cambridge centres on transforming these questions into measurable research into planetary habitability and atmospheric chemistry. He believes the discovery of life’s signatures is inevitable and that life exists beyond Earth given the vast number of planets in the universe, yet he also notes that within the Milky Way we could be the only intelligent beings aware of it.
Life Ahead, Not in the Past
Since the Industrial Revolution, humans have dramatically changed Earth’s atmosphere. Queloz believes future technology could distinguish a planet with an industrial civilization from one without, explaining that sufficiently sensitive instruments should be able to detect signs of technological activity on other worlds.
Space telescopes have advanced in infrared and visible light detection, but ultraviolet observations are still limited, especially for low-mass stars. Fudan No.1 Lancang-Mekong Future Satellite, launched last year with UV instruments, opens possibilities for new discoveries.
When a student asked why he chose astrophysics, Queloz admitted he wasn’t sure at first and even experienced “choice anxiety”.
Having excelled in physics and math in high school, he naturally pursued physics at university—but opted for astrophysics partly because he loves the outdoors. “I really like being outside. I like nature very well, so I thought astronomy is better.”
Talking about gaining success at a young age, Queloz credits curiosity and passion as his driving forces. “I keep telling everybody: follow your dreams, because life is ahead of you, not behind you. So follow your dreams,” he encouraged the students.
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Writer: LU Yulu, YANG Xinrui
Editor: WANG Mengqi, LI Yijie
