Thirty years ago this week, astronomers Michel Mayor and Didier Queloz made a groundbreaking announcement: they had discovered the first planet orbiting a Sun-like star, 51 Pegasi, a discovery later published in Nature. The finding marked the culmination of centuries of speculation and decades of searching for worlds beyond the Solar System—and it sparked a revolution in astronomy.
Since then, astronomers have confirmed over 6,000 exoplanets, with thousands more candidates awaiting verification. Observatories like NASA’s Kepler and TESS satellites, along with ground-based telescopes, have uncovered a dazzling diversity of planetary systems. From scorching “hot Jupiters” that orbit perilously close to their stars to “super-Earths” and “mini-Neptunes,” these alien worlds challenge our understanding of planetary formation. Some planets even float freely through the Galaxy, while others orbit two stars, like the fictional Tatooine of Star Wars.
Proxima Centauri: Our Closest Neighbors
Among the most intriguing exoplanets are those orbiting Proxima Centauri, just 1.3 parsecs away. Discovered in 2016, Proxima b lies within the star’s habitable zone, potentially capable of supporting liquid water, while a second planet orbits slightly farther out. “Before the end of the century, we will go there,” says Jean Schneider, an astronomer at the Paris Observatory, referring to efforts like the Breakthrough Starshot interstellar project.
TRAPPIST-1: Earth Worlds in Formation
The TRAPPIST-1 system, around 12 parsecs from Earth, hosts seven Earth-sized planets. Discovered between 2016 and 2017, some of these planets lie within the habitable zone, making the system a natural laboratory for studying planet formation and habitability. The James Webb Space Telescope continues to probe these worlds for atmospheres, with early results suggesting some may yet host conditions conducive to life. “If you were on the surface, the other planets would appear as moons in the sky—beyond sci-fi,” says Néstor Espinoza, of the Space Telescope Science Institute.
K2-138: Planets in Harmony
The K2-138 system, discovered by citizen scientists analyzing Kepler data, contains six planets in precise orbital resonances—a pattern akin to musical intervals. This unique configuration preserves clues about how planetary systems can form gradually and peacefully, unlike the chaotic early histories seen in many systems, including our own Solar System.
TOI-178: Teamwork Across Telescopes
Around 63 parsecs away, the TOI-178 system hosts six tightly packed planets, all inside Mercury’s orbit if placed in our Solar System. The discovery illustrates the power of collaboration across telescopes: TESS first identified the planets, and ESA’s Cheops satellite confirmed their arrangement. Astronomers see this as a major success of predictive planetary theory.
Kepler-47: Planets Around Twin Suns
At least two dozen circumbinary systems are known, in which planets orbit two stars. The Kepler-47 system, over 1,000 parsecs away, is a standout. One of its planets lies in the habitable zone of both stars, demonstrating that planet formation in dual-star systems can proceed similarly to single-star systems—a finding with major implications for theories of planetary evolution.
A Universe of Possibilities
“Each exoplanet is a whole brand-new world, full of possibilities and surprises,” says Jessie Christiansen, astronomer at Caltech. From planets that could be visited someday to systems that defy imagination, the past three decades have expanded our understanding of what planetary systems can look like. As astronomers continue to explore, the exoplanetary zoo promises even more discoveries, revealing a cosmos far stranger, more complex, and more beautiful than anyone could have imagined 30 years ago.
