Kapteyn c
The parameters of this planet are disputed or ambiguous in the scientific literature.
Kapteyn c is a super-Earth orbiting Kapteyn in the constellation Pictor. It lies about 13 light-years from Earth and was discovered in 2014 using the radial velocity method.
Is Kapteyn c in the Habitable Zone?
Kapteyn c orbits beyond the outer edge of the habitable zone of Kapteyn. At that distance, any surface water would almost certainly be frozen.
Habitable zone of Kapteyn: 0.090–0.232 AU (conservative: 0.114–0.220 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 Kapteyn c — one full orbit around Kapteyn — lasts 121.5 Earth days, between the years of Mercury (88 days) and Earth (365 days). It orbits at an average distance of 0.311 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.23).
How Was Kapteyn c Discovered?
Kapteyn c was discovered in 2014 using the radial velocity method, with observations from Multiple Observatories.
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 Kapteyn c?
Kapteyn c is 12.8 light-years (3.9 parsecs) from Earth. Light arriving here tonight left the planet around the year 2014. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 225,280 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. Kapteyn c scores 0.41, ranking #429 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kapteyn
Kapteyn
- Surface temperature
- 3,550 K (Sun: 5,772 K)
- Mass
- 0.28 M☉
- Radius
- 0.29 R☉
Planetary System
Kapteyn c is the only planet known to orbit Kapteyn so far.
Kapteyn c — Complete Data
| Mass (best estimate) | 7.00 Earth masses |
|---|---|
| Orbital period | 121.54 days |
| Orbital distance | 0.311 AU |
| Eccentricity | 0.230 |
| Earth Similarity Index | 0.41 |
| Distance from Earth | 12.8 light-years (3.9 parsecs) |
| Constellation | Pictor |
| Discovery method | Radial Velocity |
| Discovery facility | Multiple Observatories |
| Discovery year | 2014 |
Data: NASA Exoplanet Archive, last updated 2014-06-04. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kapteyn c
Is Kapteyn c habitable?
No — Kapteyn c orbits outside the habitable zone of Kapteyn and is likely too cold for liquid water on its surface.
How far away is Kapteyn c?
Kapteyn c is about 13 light-years from Earth in the constellation Pictor. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 225,280 years to get there.
How long is a year on Kapteyn c?
One orbit around Kapteyn takes 121.5 Earth days.
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