K2-254 c
K2-254 c is a mini-Neptune orbiting K2-254 in the constellation Virgo. It lies about 743 light-years from Earth and was discovered in 2018 using the transit method.
How Big Is K2-254 c?
K2-254 c has a radius of 2.19 times that of Earth.
Is K2-254 c in the Habitable Zone?
K2-254 c orbits inside the inner edge of the habitable zone of K2-254. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of K2-254: 0.342–0.841 AU (conservative: 0.434–0.797 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on K2-254 c
The equilibrium temperature of K2-254 c is about 551 K (278 °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 K2-254 c — one full orbit around K2-254 — lasts 12.1 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.092 AU — closer to its star than Mercury is to the Sun.
How Was K2-254 c Discovered?
K2-254 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 K2-254 c?
K2-254 c is 742.9 light-years (227.8 parsecs) from Earth. Light arriving here tonight left the planet around the year 1284. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 13,075,040 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. K2-254 c scores 0.32, ranking #1,078 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: K2-254
K2-254
- Surface temperature
- 4,629 K (Sun: 5,772 K)
- Mass
- 0.71 M☉
- Radius
- 0.67 R☉
The K2-254 Planetary System
K2-254 c is one of 2 known planets in the K2-254 system. Its siblings:
- K2-254 b (Super Earth)
K2-254 c — Complete Data
| Radius | 2.190 Earth radii (0.195 Jupiter radii) |
|---|---|
| Orbital period | 12.12 days |
| Orbital distance | 0.092 AU |
| Equilibrium temperature | 551 K (278 °C) |
| Earth Similarity Index | 0.32 |
| Distance from Earth | 742.9 light-years (227.8 parsecs) |
| Constellation | Virgo |
| Discovery method | Transit |
| Discovery facility | K2 |
| Discovery year | 2018 |
Data: NASA Exoplanet Archive, last updated 2022-03-28. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About K2-254 c
Is K2-254 c habitable?
No — K2-254 c orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is K2-254 c?
K2-254 c is about 743 light-years from Earth in the constellation Virgo. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 13,075,040 years to get there.
How big is K2-254 c compared to Earth?
K2-254 c has 2.19 times the radius of Earth.
How long is a year on K2-254 c?
One orbit around K2-254 takes 12.1 Earth days — short enough that 30 of its years would fit into one Earth year.
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