GJ 328 c
GJ 328 c is a Neptune-like planet orbiting the M0.0 star GJ 328 in the constellation Hydra. It lies about 67 light-years from Earth and was discovered in 2023 using the radial velocity method.
Is GJ 328 c in the Habitable Zone?
GJ 328 c orbits beyond the outer edge of the habitable zone of GJ 328. At that distance, any surface water would almost certainly be frozen.
Habitable zone of GJ 328: 0.234–0.596 AU (conservative: 0.297–0.565 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 328 c — one full orbit around GJ 328 — lasts 241.8 Earth days, between the years of Mercury (88 days) and Earth (365 days). It orbits at an average distance of 0.657 AU — comparable to the inner Solar System.
How Was GJ 328 c Discovered?
GJ 328 c was discovered in 2023 using the radial velocity method, with observations from Roque de los Muchachos 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 328 c?
GJ 328 c is 66.9 light-years (20.5 parsecs) from Earth. Light arriving here tonight left the planet around the year 1960. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 1,177,440 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 328 c scores 0.33, ranking #924 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: GJ 328
GJ 328
- Spectral type
- M0.0
- Surface temperature
- 3,897 K (Sun: 5,772 K)
- Mass
- 0.65 M☉
- Radius
- 0.63 R☉
- Luminosity
- 0.0832 L☉
The GJ 328 Planetary System
GJ 328 c is one of 2 known planets in the GJ 328 system. Its siblings:
- GJ 328 b (Cold Gas Giant)
GJ 328 c — Complete Data
| Mass (best estimate) | 21.40 Earth masses |
|---|---|
| Orbital period | 241.80 days |
| Orbital distance | 0.657 AU |
| Earth Similarity Index | 0.33 |
| Distance from Earth | 66.9 light-years (20.5 parsecs) |
| Constellation | Hydra |
| Discovery method | Radial Velocity |
| Discovery facility | Roque de los Muchachos Observatory |
| Discovery year | 2023 |
Data: NASA Exoplanet Archive, last updated 2023-07-10. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About GJ 328 c
Is GJ 328 c habitable?
No — GJ 328 c orbits outside the habitable zone of GJ 328 and is likely too cold for liquid water on its surface.
How far away is GJ 328 c?
GJ 328 c is about 67 light-years from Earth in the constellation Hydra. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 1,177,440 years to get there.
How long is a year on GJ 328 c?
One orbit around GJ 328 takes 241.8 Earth days.
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