What is the smallest known exoplanet?
The smallest known exoplanet is Kepler-37 b, about 0.31 times the radius of Earth: between our Moon and Mercury in size. Everything about Kepler-37 b →
| # | World | Radius | Distance |
|---|---|---|---|
| ★ 1 | Kepler-37 b | 0.31× Earth's radius | 208 ly |
| 2 | PSR B1257+12 b | 0.34× Earth's radius | 1,957 ly |
| 3 | Kepler-37 e | 0.37× Earth's radius | 208 ly |
| 4 | Kepler-879 c | 0.40× Earth's radius | 2,618 ly |
| 5 | Kepler-444 b | 0.40× Earth's radius | 119 ly |
| 6 | Kepler-158 d | 0.43× Earth's radius | 1,028 ly |
| 7 | Kepler-102 b | 0.46× Earth's radius | 352 ly |
| 8 | Kepler-444 c | 0.50× Earth's radius | 119 ly |
| 9 | Kepler-1994 b | 0.51× Earth's radius | 789 ly |
| 10 | KOI-4777.01 | 0.51× Earth's radius | 562 ly |
A transiting planet's size comes straight from geometry: the fraction of starlight it blocks. That makes the small end of the radius table one of the most trustworthy rankings on the site. Disputed rows are excluded, and so are the small bodies of our own solar system: Charon, Pluto, and our Moon are all smaller than any confirmed exoplanet, but they are not exoplanets.
What could unseat this record: space telescopes can now catch the dip from a body smaller than our Moon crossing a quiet star, so this is one of the most beatable records on the books.
Keep exploring: all records · all rocky worlds