This past Monday, October 6th, 2025, marked 30 years since the discovery of 51 Pegasi b, the first exoplanet found orbiting a sun-like star.
An exoplanet is a planet that orbits a star outside of our Solar System. 51 Pegasi b, also known as “Dimidium,” was the first exoplanet discovered orbiting a Sun-like star. It orbits 51 Pegasi, which is located in the constellation Pegasus. The gas planet was found by Mayor and Queloz using the radial velocity method, which finds exoplanets by measuring the Doppler shift in a star’s light, caused by the gravitational pull of an orbiting planet. Not only did this confirm the existence of what we now know as exoplanets, it also proved that planets could orbit closer to their stars than Mercury and paved the way for future research.
Currently, NASA’s confirmed exoplanet count is 6,022. But how have we gotten here? In the last few decades, since 51 Pegasi b’s was discovered, astronomers have developed new methods to look for more worlds beyond our solar system, one being the Kepler Space Telescope.
In 2009, NASA’s Kepler Space Telescope was launched to look for exoplanets that orbited around stars of a range of sizes. Kepler, which was retired in October 2018, found exoplanets using the transit method, which consists of looking for stars that look less bright, a result of a planet passing in front of it, called a transit. Although the KST was retired in 2018, missions like the James Webb Space Telescope are currently researching exoplanets and their atmospheres, and future missions like NASA’s Habitable Worlds Observatory and the European Space Agency’s PLATO will look for more planets orbiting stars that are potentially habitable.
As we continue to study whether life exists beyond Earth, we can study exoplanets to understand how planets exist and learn more about our universe. We can look at exoplanet weights and sizes to see differences and similarities, and better understand the diversity across our universe.
In Orbit 