What is the coolest star with a known planet?
The coolest true star known to hold planets is TRAPPIST-1, whose surface sits at about 2,566 K, less than half the Sun's temperature and cool enough to glow a deep red. Everything about TRAPPIST-1 →
| # | Star | Surface temperature | Planets |
|---|---|---|---|
| ★ 1 | TRAPPIST-1 | 2,566 K | 7 planets |
| 2 | SPECULOOS-3 | 2,800 K | 1 planet |
| 3 | 2MASS J12073346-3932539 | 2,825 K | 1 planet |
| 4 | LP 890-9 | 2,850 K | 2 planets |
| 5 | LHS 3154 | 2,861 K | 1 planet |
| 6 | Proxima Centauri | 2,900 K | 2 planets |
| 7 | G 261-6 | 2,907 K | 1 planet |
| 8 | 2MASS J03590986+2009361 | 2,943 K | 1 planet |
| 9 | GJ 1061 | 2,953 K | 3 planets |
| 10 | LP 791-18 | 2,960 K | 3 planets |
| 11 | G 192-15 | 2,999 K | 2 planets |
| 12 | TOI-6894 | 3,007 K | 1 planet |
| 13 | 2MASS J11550485-7919108 | 3,021 K | 1 planet |
| 14 | TOI-2267 B | 3,022 K | 1 planet |
| 15 | GJ 1002 | 3,024 K | 2 planets |
| 16 | GJ 682 | 3,028 K | 2 planets |
| 17 | TOI-2267 A | 3,030 K | 2 planets |
| 18 | Teegarden's Star | 3,034 K | 3 planets |
| 19 | 2MASS J02192210-3925225 | 3,064 K | 1 planet |
| 20 | TOI-1080 | 3,065 K | 1 planet |
| 21 | Kepler-42 | 3,068 K | 3 planets |
| 22 | Ross 508 | 3,071 K | 1 planet |
| 23 | TOI-1227 | 3,072 K | 1 planet |
| 24 | TOI-6008 | 3,075 K | 1 planet |
| 25 | TOI-715 | 3,075 K | 1 planet |
Showing the top 25 of 4,440 that qualify.
The bottom of this ranking runs into a definition. Below roughly 0.075 solar masses an object never gets hot enough at its core to fuse hydrogen, which makes it a brown dwarf rather than a star, and the catalog holds several such objects with companions at temperatures far below anything here. This table is held to confirmed stars, which means a measured mass above that line.
The coolest real stars are red dwarfs, and they matter out of all proportion to their size: they are the most common star in the galaxy, they burn for trillions of years, and their habitable zones sit so close in that a planet there is comparatively easy to find. The catch is that a planet that close is tidally locked and exposed to violent flares.
What is the coolest star with a known planet?
The coolest true star known to hold planets is TRAPPIST-1, whose surface sits at about 2,566 K, less than half the Sun's temperature and cool enough to glow a deep red.
What is the coolest star that has planets?
TRAPPIST-1, at about 2,566 K. It is a red dwarf, the smallest and longest-lived kind of star, and it holds 7 planets.
What is the difference between a red dwarf and a brown dwarf?
Fusion. A red dwarf is heavy enough to burn hydrogen in its core and shine steadily for trillions of years. A brown dwarf never reaches that threshold: it glows from leftover formation heat and slowly fades. The dividing line is about 0.075 times the Sun's mass, and this ranking sits above it.
Could a planet be habitable around a cool star?
Possibly, and it is one of the central questions in the field. The habitable zone of a cool star is close in, so a planet there is likely tidally locked with one permanent day side, and young red dwarfs flare hard enough to strip an atmosphere. Whether a world can hold on through that is what the next decade of observations is designed to test.
Keep exploring: all records · the TRAPPIST-1 system · the hottest star with a planet