K2-26 b
K2-26 b is a mini-Neptune orbiting the M1.0 V star K2-26 in the constellation Gemini. It lies about 323 light-years from Earth and was discovered in 2016 using the transit method.
How Big Is K2-26 b?
K2-26 b has a radius of 2.67 times that of Earth.
Is K2-26 b in the Habitable Zone?
K2-26 b orbits inside the inner edge of the habitable zone of K2-26. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of K2-26: 0.180–0.461 AU (conservative: 0.228–0.437 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on K2-26 b
The equilibrium temperature of K2-26 b is about 430 K (157 °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. It receives 5.80 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on K2-26 b — one full orbit around K2-26 — lasts 14.6 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.096 AU — closer to its star than Mercury is to the Sun.
How Was K2-26 b Discovered?
K2-26 b was discovered in 2016 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 K2-26 b?
K2-26 b is 323.1 light-years (99.1 parsecs) from Earth. Light arriving here tonight left the planet around the year 1703. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 5,686,560 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. K2-26 b scores 0.42, ranking #415 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: K2-26
K2-26
- Spectral type
- M1.0 V
- Surface temperature
- 3,785 K (Sun: 5,772 K)
- Mass
- 0.56 M☉
- Radius
- 0.52 R☉
- Luminosity
- 0.0490 L☉
- Age
- 1.0 billion years (Sun: 4.6)
Planetary System
K2-26 b is the only planet known to orbit K2-26 so far.
K2-26 b — Complete Data
| Radius | 2.670 Earth radii (0.238 Jupiter radii) |
|---|---|
| Orbital period | 14.57 days |
| Orbital distance | 0.096 AU |
| Equilibrium temperature | 430 K (157 °C) |
| Stellar irradiation | 5.80× Earth |
| Earth Similarity Index | 0.42 |
| Distance from Earth | 323.1 light-years (99.1 parsecs) |
| Constellation | Gemini |
| Discovery method | Transit |
| Discovery facility | K2 |
| Discovery year | 2016 |
Data: NASA Exoplanet Archive, last updated 2016-01-20. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About K2-26 b
Is K2-26 b habitable?
No — K2-26 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is K2-26 b?
K2-26 b is about 323 light-years from Earth in the constellation Gemini. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 5,686,560 years to get there.
How big is K2-26 b compared to Earth?
K2-26 b has 2.67 times the radius of Earth.
How long is a year on K2-26 b?
One orbit around K2-26 takes 14.6 Earth days — short enough that 25 of its years would fit into one Earth year.
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