GJ 317 b
GJ 317 b is a cold gas giant orbiting the M3.5 V star GJ 317 in the constellation Pyxis. It lies about 50 light-years from Earth and was discovered in 2007 using the radial velocity method.
Is GJ 317 b in the Habitable Zone?
GJ 317 b orbits beyond the outer edge of the habitable zone of GJ 317. At that distance, any surface water would almost certainly be frozen.
Habitable zone of GJ 317: 0.121–0.313 AU (conservative: 0.153–0.297 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 317 b — one full orbit around GJ 317 — lasts 695.7 Earth days, longer than an Earth year. It orbits at an average distance of 1.138 AU. Its orbit is mildly elliptical (eccentricity 0.08).
How Was GJ 317 b Discovered?
GJ 317 b was discovered in 2007 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 317 b?
GJ 317 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.
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 317 b scores 0.08, ranking #4,599 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: GJ 317
GJ 317
- Spectral type
- M3.5 V
- Surface temperature
- 3,496 K (Sun: 5,772 K)
- Mass
- 0.40 M☉
- Radius
- 0.40 R☉
The GJ 317 Planetary System
GJ 317 b is one of 2 known planets in the GJ 317 system. Its siblings:
- GJ 317 c (Cold Gas Giant)
GJ 317 b — Complete Data
| Mass (best estimate) | 536.49 Earth masses |
|---|---|
| Orbital period | 695.69 days |
| Orbital distance | 1.138 AU |
| Eccentricity | 0.083 |
| Earth Similarity Index | 0.08 |
| Distance from Earth | 49.6 light-years (15.2 parsecs) |
| Constellation | Pyxis |
| Discovery method | Radial Velocity |
| Discovery facility | W. M. Keck Observatory |
| Discovery year | 2007 |
Data: NASA Exoplanet Archive, last updated 2025-08-28. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About GJ 317 b
Is GJ 317 b habitable?
No — GJ 317 b orbits outside the habitable zone of GJ 317 and is likely too cold for liquid water on its surface.
How far away is GJ 317 b?
GJ 317 b is about 50 light-years from Earth in the constellation Pyxis. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 872,960 years to get there.
How long is a year on GJ 317 b?
One orbit around GJ 317 takes 695.7 Earth days.
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