K2-312 c
K2-312 c is a cold gas giant orbiting the G0 V star HD 80653 in the constellation Cancer. It lies about 358 light-years from Earth and was discovered in 2023 using the radial velocity method. It orbits within the habitable zone of its star — the region where liquid water could exist on a planet's surface.
Is K2-312 c in the Habitable Zone?
K2-312 c orbits inside the conservative habitable zone of HD 80653 — the region where a rocky planet could sustain liquid water on its surface. This makes it one of the most interesting known exoplanets in the search for life.
Habitable zone of HD 80653: 0.947–2.221 AU (conservative: 1.200–2.106 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on K2-312 c
The equilibrium temperature of K2-312 c is about 229 K (-44 °C) — well below freezing. 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 K2-312 c — one full orbit around HD 80653 — lasts 871.3 Earth days, longer than an Earth year. It orbits at an average distance of 1.882 AU. Its orbit is highly elliptical (eccentricity 0.84), swinging dramatically closer to and farther from its star.
How Was K2-312 c Discovered?
K2-312 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 K2-312 c?
K2-312 c is 358.3 light-years (109.9 parsecs) from Earth. Light arriving here tonight left the planet around the year 1668. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 6,306,080 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. K2-312 c scores 0.39, ranking #509 of 5,565 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 80653
HD 80653
- Spectral type
- G0 V
- Surface temperature
- 5,959 K (Sun: 5,772 K)
- Mass
- 1.15 M☉
- Radius
- 1.20 R☉
- Luminosity
- 1.6280 L☉
- Age
- 3.3 billion years (Sun: 4.6)
The HD 80653 Planetary System
K2-312 c is one of 2 known planets in the HD 80653 system. Its siblings:
- HD 80653 b (Lava World)
K2-312 c — Complete Data
| Mass (best estimate) | 1,681.31 Earth masses |
|---|---|
| Orbital period | 871.32 days |
| Orbital distance | 1.882 AU |
| Eccentricity | 0.844 |
| Equilibrium temperature | 229 K (-44 °C) |
| Earth Similarity Index | 0.39 |
| Distance from Earth | 358.3 light-years (109.9 parsecs) |
| Constellation | Cancer |
| Discovery method | Radial Velocity |
| Discovery facility | Roque de los Muchachos Observatory |
| Discovery year | 2023 |
Data: NASA Exoplanet Archive, last updated 2026-08-06. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About K2-312 c
Is K2-312 c habitable?
K2-312 c orbits within the habitable zone of HD 80653, the region where liquid water could exist on a planet's surface. It sits in the conservative habitable zone — the most promising region for habitability. Whether it is actually habitable depends on its atmosphere and composition, which remain unknown.
How far away is K2-312 c?
K2-312 c is about 358 light-years from Earth in the constellation Cancer. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 6,306,080 years to get there.
How long is a year on K2-312 c?
One orbit around HD 80653 takes 871.3 Earth days.
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