K2-155 c
K2-155 c is a mini-Neptune orbiting K2-155 in the constellation Taurus. It lies about 237 light-years from Earth and was discovered in 2018 using the transit method.
How Big Is K2-155 c?
K2-155 c has a radius of 2.60 times that of Earth.
Is K2-155 c in the Habitable Zone?
K2-155 c orbits inside the inner edge of the habitable zone of K2-155. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of K2-155: 0.254–0.634 AU (conservative: 0.322–0.601 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 K2-155 c
The equilibrium temperature of K2-155 c is about 583 K (310 °C) — hotter than anywhere on Earth. 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 K2-155 c — one full orbit around K2-155 — lasts 13.9 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.095 AU — closer to its star than Mercury is to the Sun.
How Was K2-155 c Discovered?
K2-155 c was discovered in 2018 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 K2-155 c?
K2-155 c is 237.4 light-years (72.8 parsecs) from Earth. Light arriving here tonight left the planet around the year 1789. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 4,178,240 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. K2-155 c scores 0.39, ranking #517 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: K2-155
K2-155
- Surface temperature
- 4,258 K (Sun: 5,772 K)
- Mass
- 0.65 M☉
- Radius
- 0.58 R☉
The K2-155 Planetary System
K2-155 c is one of 3 known planets in the K2-155 system. Its siblings:
K2-155 c — Complete Data
| Radius | 2.600 Earth radii (0.232 Jupiter radii) |
|---|---|
| Orbital period | 13.85 days |
| Orbital distance | 0.095 AU |
| Equilibrium temperature | 583 K (310 °C) |
| Earth Similarity Index | 0.39 |
| Distance from Earth | 237.4 light-years (72.8 parsecs) |
| Constellation | Taurus |
| Discovery method | Transit |
| Discovery facility | K2 |
| Discovery year | 2018 |
Data: NASA Exoplanet Archive, last updated 2018-04-25. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About K2-155 c
Is K2-155 c habitable?
No — K2-155 c orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is K2-155 c?
K2-155 c is about 237 light-years from Earth in the constellation Taurus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 4,178,240 years to get there.
How big is K2-155 c compared to Earth?
K2-155 c has 2.60 times the radius of Earth.
How long is a year on K2-155 c?
One orbit around K2-155 takes 13.9 Earth days — short enough that 26 of its years would fit into one Earth year.
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