GJ 15 A b
The parameters of this planet are disputed or ambiguous in the scientific literature.
GJ 15 A b is a super-Earth orbiting the M1 star GJ 15 A in the constellation Andromeda. It lies about 12 light-years from Earth and was discovered in 2014 using the radial velocity method.
Is GJ 15 A b in the Habitable Zone?
GJ 15 A b orbits inside the inner edge of the habitable zone of GJ 15 A. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of GJ 15 A: 0.122–0.314 AU (conservative: 0.154–0.297 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
See the full interactive habitable-zone view in the Exoplanet Explorer app ›
Orbit and Year Length
A year on GJ 15 A b — one full orbit around GJ 15 A — lasts 11.4 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.072 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.09).
How Was GJ 15 A b Discovered?
GJ 15 A b was discovered in 2014 using the radial velocity method, with observations from W. M. Keck 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 15 A b?
GJ 15 A b is 11.6 light-years (3.6 parsecs) from Earth. Light arriving here tonight left the planet around the year 2015. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 204,160 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 15 A b scores 0.53, ranking #214 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: GJ 15 A
GJ 15 A b belongs to a system of 2 stars; it orbits GJ 15 A.
GJ 15 A
- Spectral type
- M1
- Surface temperature
- 3,607 K (Sun: 5,772 K)
- Mass
- 0.38 M☉
- Radius
- 0.38 R☉
- Luminosity
- 0.0221 L☉
The GJ 15 A Planetary System
GJ 15 A b is one of 2 known planets in the GJ 15 A system. Its siblings:
- GJ 15 A c (Neptune-like)
GJ 15 A b — Complete Data
| Mass (best estimate) | 3.03 Earth masses |
|---|---|
| Orbital period | 11.44 days |
| Orbital distance | 0.072 AU |
| Eccentricity | 0.094 |
| Earth Similarity Index | 0.53 |
| Distance from Earth | 11.6 light-years (3.6 parsecs) |
| Constellation | Andromeda |
| Discovery method | Radial Velocity |
| Discovery facility | W. M. Keck Observatory |
| Discovery year | 2014 |
Data: NASA Exoplanet Archive, last updated 2019-10-02. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About GJ 15 A b
Is GJ 15 A b habitable?
No — GJ 15 A b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is GJ 15 A b?
GJ 15 A b is about 12 light-years from Earth in the constellation Andromeda. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 204,160 years to get there.
How long is a year on GJ 15 A b?
One orbit around GJ 15 A takes 11.4 Earth days — short enough that 32 of its years would fit into one Earth year.
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