K2-266 b
K2-266 b is a sub-Neptune orbiting K2-266 in the constellation Sextans. It lies about 253 light-years from Earth and was discovered in 2018 using the transit method.
How Big Is K2-266 b?
K2-266 b has a radius of 3.30 times that of Earth. Its mass is 11.3 times that of Earth.
Is K2-266 b in the Habitable Zone?
K2-266 b orbits inside the inner edge of the habitable zone of K2-266. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of K2-266: 0.312–0.779 AU (conservative: 0.395–0.738 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on K2-266 b
The equilibrium temperature of K2-266 b is about 1,515 K (1,242 °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 880 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on K2-266 b — one full orbit around K2-266 — lasts just 15.8 hours, shorter than Mercury's 88-day year. It orbits at an average distance of 0.013 AU — closer to its star than Mercury is to the Sun.
How Was K2-266 b Discovered?
K2-266 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 K2-266 b?
K2-266 b is 253.0 light-years (77.6 parsecs) from Earth. Light arriving here tonight left the planet around the year 1773. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 4,452,800 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. K2-266 b scores 0.20, ranking #3,887 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: K2-266
K2-266 b belongs to a system of 2 stars; it orbits K2-266.
K2-266
- Surface temperature
- 4,285 K (Sun: 5,772 K)
- Mass
- 0.69 M☉
- Radius
- 0.70 R☉
- Luminosity
- 0.1502 L☉
The K2-266 Planetary System
K2-266 b is one of 4 known planets in the K2-266 system. Its siblings:
K2-266 b — Complete Data
| Radius | 3.300 Earth radii (0.294 Jupiter radii) |
|---|---|
| Mass (best estimate) | 11.27 Earth masses |
| Orbital period | 0.66 days |
| Orbital distance | 0.013 AU |
| Equilibrium temperature | 1,515 K (1,242 °C) |
| Stellar irradiation | 879.50× Earth |
| Earth Similarity Index | 0.20 |
| Distance from Earth | 253.0 light-years (77.6 parsecs) |
| Constellation | Sextans |
| Discovery method | Transit |
| Discovery facility | K2 |
| Discovery year | 2018 |
Data: NASA Exoplanet Archive, last updated 2022-10-31. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About K2-266 b
Is K2-266 b habitable?
No — K2-266 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is K2-266 b?
K2-266 b is about 253 light-years from Earth in the constellation Sextans. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 4,452,800 years to get there.
How big is K2-266 b compared to Earth?
K2-266 b has 3.30 times the radius of Earth and about 11.3 times its mass.
How long is a year on K2-266 b?
One orbit around K2-266 takes 0.7 Earth days — short enough that 555 of its years would fit into one Earth year.
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