Top 10 Exoplanets Discovered by the Kepler Space Telescope

#1: Kepler-186f (Distance: ~500 light-years, Radius: ~7,500 miles)

Kepler-186f stands as a landmark discovery in exoplanetary science—it was the first Earth-sized planet found orbiting within the habitable zone of a star. Located in the Cygnus constellation, this rocky planet orbits a red dwarf star that’s smaller and cooler than our Sun. What makes Kepler-186f so compelling is its Earth-like size—just 10% larger than Earth—and its potential for liquid water. Since it receives about one-third the sunlight we do, its surface might be chilly, but greenhouse gases could tip the balance. It orbits its star every 130 days at a distance of about 32 million miles. While it likely lacks blue skies—its red dwarf host would cast a faint orange-red hue—the excitement this planet generated was palpable. In 2014, it made front-page news worldwide. Even Carl Sagan, had he lived, would have smiled at the poetic symmetry of finding a possible Earth cousin so early in Kepler’s mission.

#2: Kepler-22b (Distance: ~620 light-years, Radius: ~15,300 miles)

Kepler-22b was the first planet found in the habitable zone of a Sun-like star. Twice the size of Earth, it likely falls into the “mini-Neptune” or “water world” category. Discovered early in Kepler’s mission, this exoplanet instantly captivated scientists and the public alike. Its star is remarkably similar to our Sun, and its 290-day orbit places it at roughly 79 million miles from its star—comparable to the orbit of Venus, but in a cooler system. Some models suggest Kepler-22b may be entirely covered in ocean, with no landmasses at all. Imagine vast, endless seas under perpetual cloud cover—a planet of rainstorms and tides unlike anything on Earth. It might not be Earth 2.0, but Kepler-22b made scientists reimagine what a habitable zone planet could look like beyond our solar blueprint.

#3: Kepler-452b (Distance: ~1,400 light-years, Radius: ~10,500 miles)

Nicknamed “Earth’s older cousin,” Kepler-452b orbits a star remarkably similar to the Sun but 1.5 billion years older. Its location in the habitable zone and only 60% greater diameter than Earth initially sparked hopes of a truly Earth-like world. However, its mass suggests it may be more of a super-Earth, with higher gravity and a thicker atmosphere. Kepler-452b’s 385-day orbit is eerily close to Earth’s 365 days, and it lies around 95 million miles from its star. Scientists speculate it may once have had surface water, but it could now be entering a runaway greenhouse phase, much like Venus. The star’s advanced age adds a bittersweet tone—if life ever did exist there, it may now be dwindling or gone, making Kepler-452b a poignant reminder that habitability is not eternal.

#4: Kepler-10b (Distance: ~560 light-years, Radius: ~8,700 miles)

Kepler-10b holds the distinction of being the first rocky exoplanet confirmed by the Kepler mission. Despite its promising composition, the planet is utterly inhospitable. It lies just 1.4 million miles from its host star—so close that a year lasts only 20 hours, and daytime temperatures soar to over 3,100°F. Its sun-facing side may be a sea of molten rock, and any atmosphere would have long since been vaporized. Yet Kepler-10b is scientifically crucial. It proved that Kepler could indeed detect terrestrial worlds, not just gas giants. When its discovery was announced in 2011, it was hailed as the first “lava world,” a new category of exoplanet defined not by potential for life, but by the violence of its environment.

#5: Kepler-11 System (Distance: ~2,000 light-years, 6 planets, Sizes: ~1.9x to 4.5x Earth’s radius)

The Kepler-11 system shattered expectations by showing just how packed a planetary system could be. With six confirmed planets, all orbiting within a distance smaller than Venus’s orbit around the Sun, this system is like a cosmic game of bumper cars. These planets are relatively low-density and likely have thick gaseous envelopes. They orbit a Sun-like star, and their tight spacing led scientists to reconsider how planetary migration works. Discovered in 2011, the system remains a benchmark for compact planetary arrangements. The stability of such a configuration over billions of years is still a puzzle, and some researchers theorize that this system may have undergone a wild past of orbital reshuffling. Kepler-11 reminded astronomers that planetary systems can look radically different from our own and still thrive.

#6: Kepler-62f (Distance: ~1,200 light-years, Radius: ~9,300 miles)

Kepler-62f is part of a multi-planet system with two planets in the habitable zone, but 62f stands out for its Earth-like size and potential for life. Orbiting a star smaller and cooler than the Sun, it lies at a distance of about 40 million miles from its host, completing an orbit every 267 days. Models suggest that 62f could be a rocky world with a thick atmosphere and possibly oceans. Its host star is relatively stable, making it a prime target for future habitability studies. One thing that makes Kepler-62f special is its timing—it was discovered during a turning point in exoplanet science when finding multiple potentially habitable planets in a single system seemed almost unthinkable. It quickly became a poster child for the idea that Earth-like planets are probably common.

#7: Kepler-20e and Kepler-20f (Distance: ~950 light-years, Radii: 6,900 miles & 8,100 miles)

Discovered in 2011, Kepler-20e and 20f were the first Earth-sized planets found orbiting another star. Kepler-20f, slightly larger than Earth, orbits every 20 days; Kepler-20e, smaller than Venus, completes its year in just six days. Although both are too close to their star for habitability—surface temperatures would vaporize water—their discovery showed that Kepler could detect truly Earth-sized worlds. These planets helped shift the narrative from gas giants to rocky Earth analogs, proving that such worlds were not only out there but detectable with current technology. Their tight orbits also raised questions about planetary formation and migration, especially in systems with both large and small planets packed together.

#8: Kepler-36b and Kepler-36c (Distance: ~1,530 light-years, Radii: ~8,100 miles & ~19,500 miles)

Kepler-36b and 36c orbit incredibly close to each other, with only 1.2 million miles separating their orbits. In our solar system, that would be closer than the distance between Earth and the Moon. What’s fascinating is how different these two worlds are: Kepler-36b is rocky, about 1.5 times Earth’s size, while Kepler-36c is a Neptune-like gas giant nearly 4 times as large. Their proximity and radically different densities challenged models of planet formation. During closest approach, the planets would appear large and bright in each other’s skies—a visual marvel unlike anything seen on Earth.

#9: Kepler-438b (Distance: ~470 light-years, Radius: ~7,300 miles)

Kepler-438b is among the most Earth-like exoplanets ever discovered. Slightly larger than Earth, it orbits in the habitable zone of a red dwarf and receives about 40% more sunlight than Earth. At first glance, that might seem promising. However, its host star is active, frequently flaring with high-energy radiation that could strip away any atmosphere. Still, if Kepler-438b has a strong magnetic field, it might be able to retain its atmosphere and surface water. The tension between its Earth-like traits and its hostile environment makes it a fascinating candidate in the search for life—and a reminder that “Earth-like” doesn’t always mean “Earth-friendly.”

#10: Kepler-69c (Distance: ~2,700 light-years, Radius: ~10,100 miles)

Initially hailed as a potentially habitable planet, Kepler-69c has since been reevaluated as possibly more of a Venus analog—a super-Earth with a thick atmosphere and extreme greenhouse effect. It orbits a Sun-like star every 242 days at about 80 million miles, near the inner edge of the habitable zone. Although probably too hot for life as we know it, Kepler-69c remains important as a cautionary tale. It helped refine how astronomers define habitability—not just by orbital distance, but by considering atmosphere, star type, and other environmental factors. Its discovery sparked debate about “super-Venus” planets and their potential to masquerade as Earth-like worlds in early data.

Looking Back at Kepler’s Cosmic Legacy

The Kepler Space Telescope transformed our understanding of the galaxy. It showed us that planets are not rare but common, that Earth-sized worlds exist in habitable zones, and that solar systems come in a dazzling variety of architectures. Each of these ten exoplanets opened a new window into planetary science and inspired new questions about life in the universe. Kepler may have gone silent in 2018, but its discoveries continue to ripple through astronomy, reminding us that the stars are full of possibilities—and perhaps even neighbors we haven’t yet met.