K2-285 d
K2-285 d is a mini-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 d?
K2-285 d has a radius of 2.48 times that of Earth. Its mass is 6.5 times that of Earth.
Is K2-285 d in the Habitable Zone?
K2-285 d 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 d
The equilibrium temperature of K2-285 d is about 620 K (347 °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 24.61 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on K2-285 d — one full orbit around K2-285 — lasts 10.5 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.118 AU — closer to its star than Mercury is to the Sun.
How Was K2-285 d Discovered?
K2-285 d 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 d?
K2-285 d 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 d scores 0.28, ranking #2,347 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 d is one of 4 known planets in the K2-285 system. Its siblings:
K2-285 d — Complete Data
| Radius | 2.480 Earth radii (0.221 Jupiter radii) |
|---|---|
| Mass | 6.50 Earth masses (0.020 Jupiter masses) |
| Orbital period | 10.46 days |
| Orbital distance | 0.118 AU |
| Equilibrium temperature | 620 K (347 °C) |
| Stellar irradiation | 24.61× Earth |
| Earth Similarity Index | 0.28 |
| 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 d
Is K2-285 d habitable?
No — K2-285 d orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is K2-285 d?
K2-285 d 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 d compared to Earth?
K2-285 d has 2.48 times the radius of Earth and about 6.5 times its mass.
How long is a year on K2-285 d?
One orbit around K2-285 takes 10.5 Earth days — short enough that 35 of its years would fit into one Earth year.
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