GJ 806 c
GJ 806 c is a super-Earth orbiting the M1.5 V star GJ 806 in the constellation Cygnus. It lies about 39 light-years from Earth and was discovered in 2023 using the radial velocity method.
Is GJ 806 c in the Habitable Zone?
GJ 806 c orbits inside the inner edge of the habitable zone of GJ 806. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of GJ 806: 0.132–0.340 AU (conservative: 0.167–0.322 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on GJ 806 c
The equilibrium temperature of GJ 806 c is about 490 K (217 °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 9.50 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on GJ 806 c — one full orbit around GJ 806 — lasts 6.64 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.052 AU — closer to its star than Mercury is to the Sun.
How Was GJ 806 c Discovered?
GJ 806 c was discovered in 2023 using the radial velocity method, with observations from Multiple Observatories.
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 806 c?
GJ 806 c is 39.3 light-years (12.0 parsecs) from Earth. Light arriving here tonight left the planet around the year 1987. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 691,680 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 806 c scores 0.36, ranking #669 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: GJ 806
GJ 806
- Spectral type
- M1.5 V
- Surface temperature
- 3,600 K (Sun: 5,772 K)
- Mass
- 0.41 M☉
- Radius
- 0.41 R☉
- Luminosity
- 0.0260 L☉
- Age
- 5.0 billion years (Sun: 4.6)
The GJ 806 Planetary System
GJ 806 c is one of 2 known planets in the GJ 806 system. Its siblings:
- GJ 806 b (Super Earth)
GJ 806 c — Complete Data
| Mass (best estimate) | 5.80 Earth masses |
|---|---|
| Orbital period | 6.64 days |
| Orbital distance | 0.052 AU |
| Equilibrium temperature | 490 K (217 °C) |
| Stellar irradiation | 9.50× Earth |
| Earth Similarity Index | 0.36 |
| Distance from Earth | 39.3 light-years (12.0 parsecs) |
| Constellation | Cygnus |
| Discovery method | Radial Velocity |
| Discovery facility | Multiple Observatories |
| Discovery year | 2023 |
Data: NASA Exoplanet Archive, last updated 2023-11-28. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About GJ 806 c
Is GJ 806 c habitable?
No — GJ 806 c orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is GJ 806 c?
GJ 806 c is about 39 light-years from Earth in the constellation Cygnus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 691,680 years to get there.
How long is a year on GJ 806 c?
One orbit around GJ 806 takes 6.6 Earth days — short enough that 55 of its years would fit into one Earth year.
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