GJ 3378 b
GJ 3378 b is a super-Earth orbiting the M4 V star GJ 3378 in the constellation Camelopardalis. It lies about 25 light-years from Earth and was discovered in 2026 using the radial velocity method. It orbits within the habitable zone of its star — the region where liquid water could exist on a planet's surface.
Is GJ 3378 b in the Habitable Zone?
GJ 3378 b orbits inside the conservative habitable zone of GJ 3378 — the region where a rocky planet could sustain liquid water on its surface. This makes it one of the most interesting known exoplanets in the search for life.
Habitable zone of GJ 3378: 0.076–0.198 AU (conservative: 0.096–0.187 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on GJ 3378 b
The equilibrium temperature of GJ 3378 b is about 272 K (-1 °C) — in a range broadly comparable to Earth, whose equilibrium temperature is 255 K. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C. It receives 0.91 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on GJ 3378 b — one full orbit around GJ 3378 — lasts 21.5 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.097 AU — closer to its star than Mercury is to the Sun.
How Was GJ 3378 b Discovered?
GJ 3378 b was discovered in 2026 using the radial velocity method, with observations from Mauna Kea Observatory.
The radial velocity method measures the subtle wobble of a star caused by the gravitational pull of an orbiting planet, visible as periodic shifts in the star's light spectrum. The size of the wobble reveals the planet's minimum mass.
How Far Away Is GJ 3378 b?
GJ 3378 b is 25.2 light-years (7.7 parsecs) from Earth. Light arriving here tonight left the planet around the year 2001. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 443,520 years to make the journey.
The Host Star: GJ 3378
GJ 3378
- Spectral type
- M4 V
- Surface temperature
- 3,340 K (Sun: 5,772 K)
- Mass
- 0.26 M☉
- Radius
- 0.28 R☉
- Luminosity
- 0.0085 L☉
Planetary System
GJ 3378 b is the only planet known to orbit GJ 3378 so far.
GJ 3378 b — Complete Data
| Mass (best estimate) | 2.30 Earth masses |
|---|---|
| Orbital period | 21.45 days |
| Orbital distance | 0.097 AU |
| Equilibrium temperature | 272 K (-1 °C) |
| Stellar irradiation | 0.91× Earth |
| Distance from Earth | 25.2 light-years (7.7 parsecs) |
| Constellation | Camelopardalis |
| Discovery method | Radial Velocity |
| Discovery facility | Mauna Kea Observatory |
| Discovery year | 2026 |
Data: NASA Exoplanet Archive, last updated 2026-06-04. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About GJ 3378 b
Is GJ 3378 b habitable?
GJ 3378 b orbits within the habitable zone of GJ 3378, the region where liquid water could exist on a planet's surface. It sits in the conservative habitable zone — the most promising region for habitability. Whether it is actually habitable depends on its atmosphere and composition, which remain unknown.
How far away is GJ 3378 b?
GJ 3378 b is about 25 light-years from Earth in the constellation Camelopardalis. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 443,520 years to get there.
How long is a year on GJ 3378 b?
One orbit around GJ 3378 takes 21.5 Earth days — short enough that 17 of its years would fit into one Earth year.
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