K2-8 c
K2-8 c is a mini-Neptune orbiting the K3 V star K2-8 in the constellation Leo. It lies about 1,316 light-years from Earth and was discovered in 2016 using the transit method.
How Big Is K2-8 c?
K2-8 c has a radius of 2.41 times that of Earth.
Is K2-8 c in the Habitable Zone?
K2-8 c orbits inside the inner edge of the habitable zone of K2-8. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of K2-8: 0.414–1.007 AU (conservative: 0.525–0.955 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 ›
Temperature on K2-8 c
The equilibrium temperature of K2-8 c is about 801 K (528 °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. It receives 97.80 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on K2-8 c — one full orbit around K2-8 — lasts 5.06 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.053 AU — closer to its star than Mercury is to the Sun.
How Was K2-8 c Discovered?
K2-8 c was discovered in 2016 using the transit method, with observations from K2.
The transit method watches a star for the tiny, regular dip in brightness that occurs when a planet crosses in front of it. The depth and timing of these dips reveal the planet's size and orbital period.
How Far Away Is K2-8 c?
K2-8 c is 1,316.1 light-years (403.5 parsecs) from Earth. Light arriving here tonight left the planet about 1,316 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 23,163,360 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. K2-8 c scores 0.25, ranking #3,128 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: K2-8
K2-8
- Spectral type
- K3 V
- Surface temperature
- 4,870 K (Sun: 5,772 K)
- Mass
- 0.78 M☉
- Radius
- 0.74 R☉
The K2-8 Planetary System
K2-8 c is one of 2 known planets in the K2-8 system. Its siblings:
- K2-8 b (Sub Neptune)
K2-8 c — Complete Data
| Radius | 2.410 Earth radii (0.215 Jupiter radii) |
|---|---|
| Orbital period | 5.06 days |
| Orbital distance | 0.053 AU |
| Equilibrium temperature | 801 K (528 °C) |
| Stellar irradiation | 97.80× Earth |
| Earth Similarity Index | 0.25 |
| Distance from Earth | 1,316.1 light-years (403.5 parsecs) |
| Constellation | Leo |
| Discovery method | Transit |
| Discovery facility | K2 |
| Discovery year | 2016 |
Data: NASA Exoplanet Archive, last updated 2016-07-06. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About K2-8 c
Is K2-8 c habitable?
No — K2-8 c orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is K2-8 c?
K2-8 c is about 1,316 light-years from Earth in the constellation Leo. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 23,163,360 years to get there.
How big is K2-8 c compared to Earth?
K2-8 c has 2.41 times the radius of Earth.
How long is a year on K2-8 c?
One orbit around K2-8 takes 5.1 Earth days — short enough that 72 of its years would fit into one Earth year.
Explore K2-8 c in the app
Browse, filter and compare 6,000+ exoplanets on iPhone, iPad and Apple Watch — with habitable-zone views, widgets and offline data.
