GJ 9773 b
GJ 9773 b is a cold gas giant orbiting the M3.0 V star GJ 9773 in the constellation Pegasus. It lies about 52 light-years from Earth and was discovered in 2025 using the radial velocity method.
Is GJ 9773 b in the Habitable Zone?
GJ 9773 b orbits beyond the outer edge of the habitable zone of GJ 9773. At that distance, any surface water would almost certainly be frozen.
Habitable zone of GJ 9773: 0.110–0.286 AU (conservative: 0.140–0.271 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Orbit and Year Length
A year on GJ 9773 b — one full orbit around GJ 9773 — lasts 2,965.0 Earth days, longer than an Earth year. It orbits at an average distance of 2.921 AU. Its orbit is mildly elliptical (eccentricity 0.22).
How Was GJ 9773 b Discovered?
GJ 9773 b was discovered in 2025 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 9773 b?
GJ 9773 b is 51.9 light-years (15.9 parsecs) from Earth. Light arriving here tonight left the planet around the year 1975. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 913,440 years to make the journey.
The Host Star: GJ 9773
GJ 9773
- Spectral type
- M3.0 V
- Surface temperature
- 3,528 K (Sun: 5,772 K)
- Mass
- 0.36 M☉
- Radius
- 0.36 R☉
Planetary System
GJ 9773 b is the only planet known to orbit GJ 9773 so far.
GJ 9773 b — Complete Data
| Mass (best estimate) | 172.58 Earth masses |
|---|---|
| Orbital period | 2,965.00 days |
| Orbital distance | 2.921 AU |
| Eccentricity | 0.218 |
| Distance from Earth | 51.9 light-years (15.9 parsecs) |
| Constellation | Pegasus |
| Discovery method | Radial Velocity |
| Discovery facility | Calar Alto Observatory |
| Discovery year | 2025 |
Data: NASA Exoplanet Archive, last updated 2025-08-28. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About GJ 9773 b
Is GJ 9773 b habitable?
No — GJ 9773 b orbits outside the habitable zone of GJ 9773 and is likely too cold for liquid water on its surface.
How far away is GJ 9773 b?
GJ 9773 b is about 52 light-years from Earth in the constellation Pegasus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 913,440 years to get there.
How long is a year on GJ 9773 b?
One orbit around GJ 9773 takes 2,965.0 Earth days.
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