First exoplanet discovered Two Swiss scientists shook up astronomy 30 years ago
When two Swiss researchers discovered an alien planet outside our solar system in 1995, hardly anyone believed them at first - today their discovery is considered the starting signal for the search for life in space.
06.10.2025, 18:25
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- In 1995, Swiss astronomers Didier Queloz and Michel Mayor discovered the first exoplanet with their measuring instrument "Elodie".
- The result was initially met with great skepticism, but ultimately earned the researchers the Nobel Prize in Physics in 2019.
- The discovery led to a paradigm shift in astronomy - around 6,000 exoplanets are now known.
Thirty years ago, the Swiss Didier Queloz and Michel Mayor turned astronomy on its head: on October 6, 1995, they announced the first discovery of a planet outside our solar system at a conference in Florence.
"I was completely stunned when I saw the data," recalls Queloz of the discovery of the planet 51 Pegasi b, for which he was awarded the Nobel Prize in Physics in 2019. At the time, Queloz was a doctoral student with Professor Michel Mayor at the University of Geneva. The two spent several years building Elodie, a new machine to detect objects in orbits around other stars.
At the time, the researchers did not believe that they would ever find a planet. "Michel was so sure that he even went on vacation, gave me the keys to the telescope and said: All right, just get started," says Queloz.
"I think I've found a planet"
But as soon as Queloz had started taking measurements, the data pointed to something completely unexpected. "Even during the first observations of 51 Pegasi, I noticed that the speed of the star changed regularly," recalls Queloz. "At first I thought it must be a fault in the instrument. He worked hard to find the fault. "Of course I didn't tell Michel - I wanted to solve the problem first."
At some point, he realized that there was no technical explanation for the fault. "So I asked myself: could it be an object in orbit after all?" Step by step, he found an orbit in the data that would exactly match a planet - one that only needed four days to orbit its star. "So I wrote to Michel: 'I think I've found a planet'." The professor responded kindly. "He later told me that he didn't believe a word I said."
A lot of skepticism from the experts
But Queloz was proved right. Mayor also found no other explanation for the data. Repeated measurements confirmed the assumption. The planet actually existed. So the two researchers submitted an article on their spectacular discovery to the journal "Nature" for publication and presented their findings at a specialist conference in Florence.
Reactions among experts were initially skeptical. Nobody knew whether so-called exoplanets, i.e. planets outside our solar system, really existed. "There had also been many false reports about exoplanets in previous years, so the community was very cautious," explains Queloz.
Furthermore, according to the theories of the time, 51 Pegasi b should not have existed at all - and not only because it was the first exoplanet to be detected. It is relatively large, about half the size of Jupiter, and is very close to its sun. According to theories, such large planets should have been in a much more distant orbit.
US researchers wanted to find out more and pointed their own telescope at the solar system 51 Pegasi. They also discovered the planet. According to Queloz, this independent confirmation by other research teams was decisive in finally acknowledging the discovery.
Search for extraterrestrial life
According to Queloz, the discovery was a revolution for astronomy. "Since then, we no longer consider our solar system to be isolated," says the researcher. The exoplanet has shown that planets can also look very different from the planets in our own solar system. 6000 other exoplanets have been discovered since then.
Queloz was surprised by the great public interest in the discovery. "At the time, we hadn't yet realized that when you talk about a planet, people immediately start dreaming about extraterrestrial life," says Queloz. This was particularly surprising for Queloz because the conditions on 51 Pegasi b are anything but life-friendly, with temperatures of over 1000 degrees Celsius.
Nevertheless, Queloz also believes in extraterrestrial life. "The question is not whether we will find life, but how and when," he says.
Today, the 59-year-old is the director of a center at ETH Zurich that investigates the origin and spread of life on and off Earth. His former professor, 83-year-old Mayor, is now retired.
