The first confirmed Exoplanet orbiting a Sun-like star revealed a world unlike anything in our solar system, and opened the search for thousands more.
THE UNIVERSAL RECORD
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Brad Socha | October 6, 2026 | 4:59 AM EST
On October 6, 1995, Swiss astronomers Michel Mayor and Didier Queloz announced the discovery of 51 Pegasi b, the first confirmed planet found orbiting a Sun-like star beyond our solar system. The announcement, made at a scientific conference in Florence, Italy, transformed the search for other worlds from a field marked by uncertain claims into one of modern astronomy’s most productive areas.
The distinction matters. Astronomers Aleksander Wolszczan and Dale Frail had already announced planets in 1992 orbiting PSR B1257+12, a pulsar, the dense, rapidly rotating remnant of an exploded star. Those were the first confirmed planets known beyond our solar system. What Mayor and Queloz found was different: compelling evidence that a relatively ordinary star like the Sun could also possess a planet.
The planet itself made the discovery even more surprising.
51 Pegasi b was nothing like astronomers had expected.
A Planet Where Few Expected One
Mayor, a professor at the University of Geneva, and Queloz, then his doctoral student, detected the planet using the ELODIE spectrograph at the Observatoire de Haute-Provence in southern France.
They did not photograph the planet. Instead, they measured tiny changes in the motion of its host star, 51 Pegasi, located about 50 light-years away in the constellation Pegasus.
A planet and its star orbit a common centre of mass. As an unseen planet gravitationally pulls its star slightly toward and away from Earth, the star’s spectrum shifts by a minute amount. This technique, known as the radial-velocity method, allowed Mayor and Queloz to infer the presence of an orbiting companion.
Their measurements revealed something extraordinary.
The planet completed an orbit in only about 4.23 Earth days and travelled approximately 0.05 astronomical units from its star, far closer than Mercury orbits the Sun. The original observations indicated a minimum mass of roughly half that of Jupiter.
At the time, theories of giant-planet formation were strongly influenced by our own solar system, where Jupiter and Saturn orbit far from the Sun. Finding a giant planet almost pressed against its star presented astronomers with a major puzzle.
51 Pegasi b became the prototype of a class now known as hot Jupiters: gas giants orbiting extremely close to their stars.
Its strange properties initially contributed to skepticism. But American astronomers Geoffrey Marcy and R. Paul Butler independently observed 51 Pegasi shortly after the announcement and confirmed the periodic stellar motion. Later observations further strengthened the planetary interpretation.
The discovery also forced scientists to reconsider how planetary systems form and evolve. A giant planet could probably not have formed under the conditions found so close to 51 Pegasi. One explanation developed in response was planetary migration: giant planets can form farther from their stars and subsequently move inward through interactions with the material surrounding the young star.
Our solar system was no longer an adequate template for imagining every planetary system.
From 51 Pegasi b to Thousands of Worlds
The discovery opened the floodgates.
Other planets were soon detected around ordinary stars, including additional hot Jupiters. Improvements in radial-velocity instruments allowed astronomers to measure progressively smaller stellar motions, while other detection techniques dramatically expanded the search.
NASA’s Kepler space telescope, launched in 2009, transformed the field by monitoring stars for tiny decreases in brightness caused when planets crossed in front of them. The Transiting Exoplanet Survey Satellite, or TESS, later extended the search across much of the sky. The James Webb Space Telescope is now capable of examining the atmospheres of some distant worlds.
In September 2025, NASA’s official tally reached 6,000 confirmed exoplanets. By 2026, the count had exceeded 6,200, with thousands of additional candidates still awaiting confirmation.
The catalogue now includes worlds that would have seemed extraordinary in 1995: rocky planets approximately Earth’s size, super-Earths larger than our planet but smaller than Neptune, planets orbiting two stars, extremely hot worlds with very short years and planetary systems packed into remarkably small regions around their stars.
51 Pegasi b itself remains an important object of study. Later observations refined its orbital period to approximately 4.2308 days and placed it about 0.052 astronomical units from its star. In 2015, astronomers using ESO’s HARPS instrument reported detecting visible light reflected from the planet’s system, demonstrating another technique for studying distant worlds.
Recognition for the original discovery ultimately reached astronomy’s highest level.
In 2019, the Nobel Prize in Physics was divided between three scientists. James Peebles received half for theoretical discoveries in physical cosmology. The other half was awarded jointly to Mayor and Queloz “for the discovery of an exoplanet orbiting a solar-type star.”
The significance of 51 Pegasi b was not that it was the first evidence humanity had ever obtained for a planet outside the solar system. The pulsar planets came earlier, and other potential planetary companions had been proposed before 1995.
Its importance was that it provided a convincing demonstration of a planet orbiting a star broadly comparable to our Sun — and showed that planetary systems could look profoundly different from our own.
Before the discovery, astronomers could reasonably suspect that planets around ordinary stars were common. After it, they had a confirmed example.
Three decades later, thousands of known exoplanets have transformed the question. Astronomers are no longer simply asking whether other stars possess planets. They are investigating what those planets are made of, how their systems formed, what their atmospheres contain and whether some could provide environments capable of supporting life.
The first world that opened that new chapter was not another Earth.
It was the unexpected, intensely hot giant orbiting 51 Pegasi every 4.2 days.
Sources:
European Southern Observatory — 2019 Nobel Prize in Physics Awarded for Discovery of Exoplanet Orbiting a Solar-type Star
https://www.hq.eso.org/public/announcements/ann19049/
University of Geneva — Michel Mayor and Didier Queloz, Physics Nobel Prize Laureates
https://www.unige.ch/sciences/astro/en/news/michel-mayor-et-didier-queloz-laureats-du-prix-nobel-de-physique
NASA Exoplanet Archive — 51 Pegasi System Overview
https://exoplanetarchive.ipac.caltech.edu/overview/51%20Peg
NASA Science — 51 Pegasi b
https://science.nasa.gov/exoplanet-catalog/51-pegasi-b/
NASA Science — 30 Years of Exoplanets
https://science.nasa.gov/exoplanets/30-years-of-exoplanets-compilation/
NASA Science — Will the Real “First Exoplanet” Please Stand Up?
https://science.nasa.gov/universe/exoplanets/will-the-real-first-exoplanet-please-stand-up/
NASA Science — How Many Exoplanets Are There?
https://science.nasa.gov/exoplanets/how-many-exoplanets-are-there/
NASA — Extreme Planets: The PSR B1257+12 Pulsar Planet System
https://www.nasa.gov/image-article/extreme-planets/
European Southern Observatory — First Detection of Reflected Visible Light from 51 Pegasi b
https://www.eso.org/public/news/eso1517/
The Nobel Prize — The Nobel Prize in Physics 2019
https://www.nobelprize.org/prizes/physics/2019/press-release/
Nature — Orbital Migration of the Planetary Companion of 51 Pegasi to Its Present Location
https://www.nature.com/articles/380606a0
Nature — Further Evidence for the Planet Around 51 Pegasi
https://www.nature.com/articles/34369
About the Author
Brad Socha is the founder of The Universal Record, focused on sourced, factual global reporting. Coverage includes international news, geopolitics, technology, and major developments.