GJ 3988 b
GJ 3988 b is a super-Earth orbiting the M4.5 V star GJ 3988 in the constellation Draco. It lies about 32 light-years from Earth and was discovered in 2023 using the radial velocity method.
Is GJ 3988 b in the Habitable Zone?
GJ 3988 b orbits inside the inner edge of the habitable zone of GJ 3988. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of GJ 3988: 0.052–0.137 AU (conservative: 0.066–0.129 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on GJ 3988 b
The equilibrium temperature of GJ 3988 b is about 348 K (75 °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 2.45 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on GJ 3988 b — one full orbit around GJ 3988 — lasts 6.94 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.041 AU — closer to its star than Mercury is to the Sun.
How Was GJ 3988 b Discovered?
GJ 3988 b was discovered in 2023 using the radial velocity method, with observations from Calar Alto 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 3988 b?
GJ 3988 b is 32.3 light-years (9.9 parsecs) from Earth. Light arriving here tonight left the planet around the year 1994. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 568,480 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 3988 b scores 0.65, ranking #101 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: GJ 3988
GJ 3988
- Spectral type
- M4.5 V
- Surface temperature
- 3,273 K (Sun: 5,772 K)
- Mass
- 0.18 M☉
- Radius
- 0.20 R☉
- Luminosity
- 0.0040 L☉
Planetary System
GJ 3988 b is the only planet known to orbit GJ 3988 so far.
GJ 3988 b — Complete Data
| Mass (best estimate) | 3.69 Earth masses |
|---|---|
| Orbital period | 6.94 days |
| Orbital distance | 0.041 AU |
| Equilibrium temperature | 348 K (75 °C) |
| Stellar irradiation | 2.45× Earth |
| Earth Similarity Index | 0.65 |
| Distance from Earth | 32.3 light-years (9.9 parsecs) |
| Constellation | Draco |
| Discovery method | Radial Velocity |
| Discovery facility | Calar Alto Observatory |
| Discovery year | 2023 |
Data: NASA Exoplanet Archive, last updated 2023-10-21. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About GJ 3988 b
Is GJ 3988 b habitable?
No — GJ 3988 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is GJ 3988 b?
GJ 3988 b is about 32 light-years from Earth in the constellation Draco. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 568,480 years to get there.
How long is a year on GJ 3988 b?
One orbit around GJ 3988 takes 6.9 Earth days — short enough that 53 of its years would fit into one Earth year.
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