GJ 1214 b
GJ 1214 b is a mini-Neptune orbiting GJ 1214 in the constellation Ophiuchus. It lies about 48 light-years from Earth and was discovered in 2009 using the transit method.
How Big Is GJ 1214 b?
GJ 1214 b has a radius of 2.73 times that of Earth. Its mass is 8.4 times that of Earth, giving it a density of 2.26 g/cm³ — between that of rocky and gaseous planets.
Is GJ 1214 b in the Habitable Zone?
GJ 1214 b orbits inside the inner edge of the habitable zone of GJ 1214. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of GJ 1214: 0.051–0.136 AU (conservative: 0.065–0.129 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on GJ 1214 b
The equilibrium temperature of GJ 1214 b is about 567 K (294 °C) — hotter than anywhere on Earth. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C. It receives 17.20 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on GJ 1214 b — one full orbit around GJ 1214 — lasts just 37.9 hours, shorter than Mercury's 88-day year. It orbits at an average distance of 0.015 AU — closer to its star than Mercury is to the Sun. Its orbit is nearly circular (eccentricity 0.006).
How Was GJ 1214 b Discovered?
GJ 1214 b was discovered in 2009 using the transit method, with observations from MEarth Project.
The transit method watches a star for the tiny, regular dip in brightness that occurs when a planet crosses in front of it. The depth and timing of these dips reveal the planet's size and orbital period.
How Far Away Is GJ 1214 b?
GJ 1214 b is 47.8 light-years (14.6 parsecs) from Earth. Light arriving here tonight left the planet around the year 1979. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 841,280 years to make the journey.
Earth Similarity Index
The Earth Similarity Index (ESI) scores how physically similar a planet is to Earth, from 0 to 1, based on radius, density, escape velocity and surface temperature. GJ 1214 b scores 0.28, ranking #2,306 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: GJ 1214
GJ 1214
- Surface temperature
- 3,101 K (Sun: 5,772 K)
- Mass
- 0.18 M☉
- Radius
- 0.22 R☉
- Luminosity
- 0.0039 L☉
Planetary System
GJ 1214 b is the only planet known to orbit GJ 1214 so far.
GJ 1214 b — Complete Data
| Radius | 2.733 Earth radii (0.244 Jupiter radii) |
|---|---|
| Mass | 8.41 Earth masses (0.026 Jupiter masses) |
| Density | 2.26 g/cm³ (Earth: 5.51) |
| Orbital period | 1.58 days |
| Orbital distance | 0.015 AU |
| Eccentricity | 0.006 |
| Equilibrium temperature | 567 K (294 °C) |
| Stellar irradiation | 17.20× Earth |
| Earth Similarity Index | 0.28 |
| Distance from Earth | 47.8 light-years (14.6 parsecs) |
| Constellation | Ophiuchus |
| Discovery method | Transit |
| Discovery facility | MEarth Project |
| Discovery year | 2009 |
Data: NASA Exoplanet Archive, last updated 2025-10-30. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About GJ 1214 b
Is GJ 1214 b habitable?
No — GJ 1214 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is GJ 1214 b?
GJ 1214 b is about 48 light-years from Earth in the constellation Ophiuchus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 841,280 years to get there.
How big is GJ 1214 b compared to Earth?
GJ 1214 b has 2.73 times the radius of Earth and about 8.4 times its mass.
How long is a year on GJ 1214 b?
One orbit around GJ 1214 takes 1.6 Earth days — short enough that 231 of its years would fit into one Earth year.
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