HD 217107 c
HD 217107 c is a cold gas giant orbiting the G star HD 217107 in the constellation Pisces. It lies about 65 light-years from Earth and was discovered in 2005 using the radial velocity method.
Is HD 217107 c in the Habitable Zone?
The position of HD 217107 c relative to the habitable zone of HD 217107 cannot be precisely determined from the available orbital data.
Orbit and Year Length
A year on HD 217107 c — one full orbit around HD 217107 — lasts 5,138.7 Earth days, longer than Jupiter's 12-year orbit. It orbits at an average distance of 5.922 AU. Its orbit is highly elliptical (eccentricity 0.39), swinging dramatically closer to and farther from its star.
How Was HD 217107 c Discovered?
HD 217107 c was discovered in 2005 using the radial velocity method, with observations from Lick 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 HD 217107 c?
HD 217107 c is 65.4 light-years (20.1 parsecs) from Earth. Light arriving here tonight left the planet around the year 1961. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 1,151,040 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. HD 217107 c scores 0.12, ranking #4,336 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 217107
HD 217107
- Spectral type
- G
- Mass
- 1.05 M☉
- Radius
- 1.22 R☉
- Age
- 11.9 billion years (Sun: 4.6)
The HD 217107 Planetary System
HD 217107 c is one of 2 known planets in the HD 217107 system. Its siblings:
- HD 217107 b (Hot Jupiter)
HD 217107 c — Complete Data
| Mass | 1,388.91 Earth masses (4.370 Jupiter masses) |
|---|---|
| Orbital period | 5,138.70 days |
| Orbital distance | 5.922 AU |
| Eccentricity | 0.392 |
| Earth Similarity Index | 0.12 |
| Distance from Earth | 65.4 light-years (20.1 parsecs) |
| Constellation | Pisces |
| Discovery method | Radial Velocity |
| Discovery facility | Lick Observatory |
| Discovery year | 2005 |
Data: NASA Exoplanet Archive, last updated 2026-03-12. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 217107 c
Is HD 217107 c habitable?
HD 217107 c is not known to orbit within the habitable zone of HD 217107, and as a cold gas giant it is an unlikely candidate for life as we know it.
How far away is HD 217107 c?
HD 217107 c is about 65 light-years from Earth in the constellation Pisces. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 1,151,040 years to get there.
How long is a year on HD 217107 c?
One orbit around HD 217107 takes 5,138.7 Earth days.
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