K2-111 c
K2-111 c is a Neptune-like planet orbiting the G2 star K2-111 in the constellation Taurus. It lies about 654 light-years from Earth and was discovered in 2020 using the radial velocity method.
Is K2-111 c in the Habitable Zone?
K2-111 c orbits inside the inner edge of the habitable zone of K2-111. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of K2-111: 0.937–2.208 AU (conservative: 1.187–2.094 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on K2-111 c
The equilibrium temperature of K2-111 c is about 923 K (650 °C) — hot enough to melt many metals. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C.
Orbit and Year Length
A year on K2-111 c — one full orbit around K2-111 — lasts 15.7 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.116 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.07).
How Was K2-111 c Discovered?
K2-111 c was discovered in 2020 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 K2-111 c?
K2-111 c is 653.6 light-years (200.4 parsecs) from Earth. Light arriving here tonight left the planet around the year 1373. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 11,503,360 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. K2-111 c scores 0.21, ranking #3,784 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: K2-111
K2-111
- Spectral type
- G2
- Surface temperature
- 5,775 K (Sun: 5,772 K)
- Mass
- 0.84 M☉
- Radius
- 1.25 R☉
- Age
- 12.3 billion years (Sun: 4.6)
The K2-111 Planetary System
K2-111 c is one of 2 known planets in the K2-111 system. Its siblings:
- K2-111 b (Super Earth)
K2-111 c — Complete Data
| Mass (best estimate) | 11.10 Earth masses |
|---|---|
| Orbital period | 15.67 days |
| Orbital distance | 0.116 AU |
| Eccentricity | 0.069 |
| Equilibrium temperature | 923 K (650 °C) |
| Earth Similarity Index | 0.21 |
| Distance from Earth | 653.6 light-years (200.4 parsecs) |
| Constellation | Taurus |
| Discovery method | Radial Velocity |
| Discovery facility | Multiple Observatories |
| Discovery year | 2020 |
Data: NASA Exoplanet Archive, last updated 2026-04-16. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About K2-111 c
Is K2-111 c habitable?
No — K2-111 c orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is K2-111 c?
K2-111 c is about 654 light-years from Earth in the constellation Taurus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 11,503,360 years to get there.
How long is a year on K2-111 c?
One orbit around K2-111 takes 15.7 Earth days — short enough that 23 of its years would fit into one Earth year.
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