HD 187123 c
HD 187123 c is a cold gas giant orbiting HD 187123 in the constellation Cygnus. It lies about 150 light-years from Earth and was discovered in 2008 using the radial velocity method.
Is HD 187123 c in the Habitable Zone?
HD 187123 c orbits beyond the outer edge of the habitable zone of HD 187123. At that distance, any surface water would almost certainly be frozen.
Habitable zone of HD 187123: 0.868–2.045 AU (conservative: 1.100–1.938 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Orbit and Year Length
A year on HD 187123 c — one full orbit around HD 187123 — lasts 3,810.0 Earth days, longer than an Earth year. It orbits at an average distance of 4.890 AU. Its orbit is mildly elliptical (eccentricity 0.25).
How Was HD 187123 c Discovered?
HD 187123 c was discovered in 2008 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 HD 187123 c?
HD 187123 c is 149.9 light-years (46.0 parsecs) from Earth. Light arriving here tonight left the planet around the year 1877. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 2,638,240 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 187123 c scores 0.12, ranking #4,314 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 187123
HD 187123
- Surface temperature
- 5,790 K (Sun: 5,772 K)
- Mass
- 1.04 M☉
- Radius
- 1.15 R☉
- Luminosity
- 1.3401 L☉
The HD 187123 Planetary System
HD 187123 c is one of 2 known planets in the HD 187123 system. Its siblings:
- HD 187123 b (Hot Jupiter)
HD 187123 c — Complete Data
| Mass (best estimate) | 632.46 Earth masses |
|---|---|
| Orbital period | 3,810.00 days |
| Orbital distance | 4.890 AU |
| Eccentricity | 0.252 |
| Earth Similarity Index | 0.12 |
| Distance from Earth | 149.9 light-years (46.0 parsecs) |
| Constellation | Cygnus |
| Discovery method | Radial Velocity |
| Discovery facility | W. M. Keck Observatory |
| Discovery year | 2008 |
Data: NASA Exoplanet Archive, last updated 2014-07-23. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 187123 c
Is HD 187123 c habitable?
No — HD 187123 c orbits outside the habitable zone of HD 187123 and is likely too cold for liquid water on its surface.
How far away is HD 187123 c?
HD 187123 c is about 150 light-years from Earth in the constellation Cygnus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 2,638,240 years to get there.
How long is a year on HD 187123 c?
One orbit around HD 187123 takes 3,810.0 Earth days.
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