K2-263 b
K2-263 b is a super-Earth orbiting the G9 V star K2-263 in the constellation Cancer. It lies about 530 light-years from Earth and was discovered in 2018 using the transit method.
How Big Is K2-263 b?
K2-263 b has a radius of 2.51 times that of Earth. Its mass is 15.4 times that of Earth, giving it a density of 5.65 g/cm³ — comparable to rocky planets like Earth (5.51 g/cm³).
Is K2-263 b in the Habitable Zone?
K2-263 b orbits inside the inner edge of the habitable zone of K2-263. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of K2-263: 0.570–1.359 AU (conservative: 0.722–1.289 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on K2-263 b
The equilibrium temperature of K2-263 b is about 482 K (209 °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 K2-263 b — one full orbit around K2-263 — lasts 50.8 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.257 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.08).
How Was K2-263 b Discovered?
K2-263 b 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 K2-263 b?
K2-263 b is 529.9 light-years (162.5 parsecs) from Earth. Light arriving here tonight left the planet around the year 1497. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 9,326,240 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. K2-263 b scores 0.37, ranking #616 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: K2-263
K2-263
- Spectral type
- G9 V
- Surface temperature
- 5,368 K (Sun: 5,772 K)
- Mass
- 0.88 M☉
- Radius
- 0.85 R☉
- Luminosity
- 0.5500 L☉
- Age
- 7.0 billion years (Sun: 4.6)
Planetary System
K2-263 b is the only planet known to orbit K2-263 so far.
K2-263 b — Complete Data
| Radius | 2.513 Earth radii (0.224 Jupiter radii) |
|---|---|
| Mass | 15.40 Earth masses (0.048 Jupiter masses) |
| Density | 5.65 g/cm³ (Earth: 5.51) |
| Orbital period | 50.82 days |
| Orbital distance | 0.257 AU |
| Eccentricity | 0.080 |
| Equilibrium temperature | 482 K (209 °C) |
| Earth Similarity Index | 0.37 |
| Distance from Earth | 529.9 light-years (162.5 parsecs) |
| Constellation | Cancer |
| Discovery method | Transit |
| Discovery facility | K2 |
| Discovery year | 2018 |
Data: NASA Exoplanet Archive, last updated 2026-04-16. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About K2-263 b
Is K2-263 b habitable?
No — K2-263 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is K2-263 b?
K2-263 b is about 530 light-years from Earth in the constellation Cancer. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 9,326,240 years to get there.
How big is K2-263 b compared to Earth?
K2-263 b has 2.51 times the radius of Earth and about 15.4 times its mass.
How long is a year on K2-263 b?
One orbit around K2-263 takes 50.8 Earth days.
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