GJ 238 b
GJ 238 b is a terrestrial planet orbiting the M2.5 V star GJ 238 in the constellation Pictor. It lies about 50 light-years from Earth and was discovered in 2024 using the transit method.
How Big Is GJ 238 b?
GJ 238 b has a radius of 0.57 times that of Earth.
Is GJ 238 b in the Habitable Zone?
GJ 238 b orbits inside the inner edge of the habitable zone of GJ 238. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of GJ 238: 0.127–0.330 AU (conservative: 0.161–0.313 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on GJ 238 b
The equilibrium temperature of GJ 238 b is about 758 K (485 °C) — hot enough to melt many metals. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C.
Orbit and Year Length
A year on GJ 238 b — one full orbit around GJ 238 — lasts just 41.9 hours, shorter than Mercury's 88-day year. It orbits at an average distance of 0.021 AU — closer to its star than Mercury is to the Sun.
How Was GJ 238 b Discovered?
GJ 238 b was discovered in 2024 using the transit method, with observations from Transiting Exoplanet Survey Satellite (TESS).
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 238 b?
GJ 238 b is 49.6 light-years (15.2 parsecs) from Earth. Light arriving here tonight left the planet around the year 1977. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 872,960 years to make the journey.
The Host Star: GJ 238
GJ 238
- Spectral type
- M2.5 V
- Surface temperature
- 3,485 K (Sun: 5,772 K)
- Mass
- 0.42 M☉
- Radius
- 0.43 R☉
- Luminosity
- 0.0242 L☉
Planetary System
GJ 238 b is the only planet known to orbit GJ 238 so far.
GJ 238 b — Complete Data
| Radius | 0.566 Earth radii (0.050 Jupiter radii) |
|---|---|
| Orbital period | 1.74 days |
| Orbital distance | 0.021 AU |
| Equilibrium temperature | 758 K (485 °C) |
| Distance from Earth | 49.6 light-years (15.2 parsecs) |
| Constellation | Pictor |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2024 |
Data: NASA Exoplanet Archive, last updated 2024-08-07. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About GJ 238 b
Is GJ 238 b habitable?
No — GJ 238 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is GJ 238 b?
GJ 238 b is about 50 light-years from Earth in the constellation Pictor. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 872,960 years to get there.
How big is GJ 238 b compared to Earth?
GJ 238 b has 0.57 times the radius of Earth.
How long is a year on GJ 238 b?
One orbit around GJ 238 takes 1.7 Earth days — short enough that 209 of its years would fit into one Earth year.
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