K2-285 c
K2-285 c is a sub-Neptune orbiting the K2 V star K2-285 in the constellation Pisces. It lies about 505 light-years from Earth and was discovered in 2018 using the transit method.
How Big Is K2-285 c?
K2-285 c has a radius of 3.53 times that of Earth. Its mass is 15.7 times that of Earth, giving it a density of 1.95 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is K2-285 c in the Habitable Zone?
K2-285 c orbits inside the inner edge of the habitable zone of K2-285. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of K2-285: 0.458–1.107 AU (conservative: 0.580–1.050 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on K2-285 c
The equilibrium temperature of K2-285 c is about 741 K (468 °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 50.35 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on K2-285 c — one full orbit around K2-285 — lasts 7.14 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.082 AU — closer to its star than Mercury is to the Sun.
How Was K2-285 c Discovered?
K2-285 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 K2-285 c?
K2-285 c is 505.4 light-years (155.0 parsecs) from Earth. Light arriving here tonight left the planet around the year 1521. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 8,895,040 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. K2-285 c scores 0.21, ranking #3,749 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: K2-285
K2-285
- Spectral type
- K2 V
- Surface temperature
- 4,975 K (Sun: 5,772 K)
- Mass
- 0.83 M☉
- Radius
- 0.79 R☉
The K2-285 Planetary System
K2-285 c is one of 4 known planets in the K2-285 system. Its siblings:
K2-285 c — Complete Data
| Radius | 3.530 Earth radii (0.315 Jupiter radii) |
|---|---|
| Mass | 15.68 Earth masses (0.049 Jupiter masses) |
| Density | 1.95 g/cm³ (Earth: 5.51) |
| Orbital period | 7.14 days |
| Orbital distance | 0.082 AU |
| Equilibrium temperature | 741 K (468 °C) |
| Stellar irradiation | 50.35× Earth |
| Earth Similarity Index | 0.21 |
| Distance from Earth | 505.4 light-years (155.0 parsecs) |
| Constellation | Pisces |
| Discovery method | Transit |
| Discovery facility | K2 |
| Discovery year | 2018 |
Data: NASA Exoplanet Archive, last updated 2018-12-11. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About K2-285 c
Is K2-285 c habitable?
No — K2-285 c orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is K2-285 c?
K2-285 c is about 505 light-years from Earth in the constellation Pisces. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 8,895,040 years to get there.
How big is K2-285 c compared to Earth?
K2-285 c has 3.53 times the radius of Earth and about 15.7 times its mass.
How long is a year on K2-285 c?
One orbit around K2-285 takes 7.1 Earth days — short enough that 51 of its years would fit into one Earth year.
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