K2-27 b
K2-27 b is a Neptune-like planet orbiting K2-27 in the constellation Leo. It lies about 814 light-years from Earth and was discovered in 2016 using the transit method.
How Big Is K2-27 b?
K2-27 b has a radius of 4.74 times that of Earth. Its mass is 30.2 times that of Earth, giving it a density of 1.71 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is K2-27 b in the Habitable Zone?
The position of K2-27 b relative to the habitable zone of K2-27 cannot be precisely determined from the available orbital data.
Habitable zone of K2-27: 0.559–1.338 AU (conservative: 0.708–1.269 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on K2-27 b
The equilibrium temperature of K2-27 b is about 836 K (563 °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 116 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on K2-27 b — one full orbit around K2-27 — lasts 6.77 Earth days, shorter than Mercury's 88-day year.
How Was K2-27 b Discovered?
K2-27 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 K2-27 b?
K2-27 b is 814.2 light-years (249.6 parsecs) from Earth. Light arriving here tonight left the planet around the year 1212. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 14,329,920 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. K2-27 b scores 0.17, ranking #4,085 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: K2-27
K2-27 b belongs to a system of 3 stars; it orbits K2-27.
K2-27
- Surface temperature
- 5,246 K (Sun: 5,772 K)
- Mass
- 0.88 M☉
- Radius
- 0.88 R☉
Planetary System
K2-27 b is the only planet known to orbit K2-27 so far.
K2-27 b — Complete Data
| Radius | 4.740 Earth radii (0.423 Jupiter radii) |
|---|---|
| Mass | 30.20 Earth masses (0.095 Jupiter masses) |
| Density | 1.71 g/cm³ (Earth: 5.51) |
| Orbital period | 6.77 days |
| Equilibrium temperature | 836 K (563 °C) |
| Stellar irradiation | 116.00× Earth |
| Earth Similarity Index | 0.17 |
| Distance from Earth | 814.2 light-years (249.6 parsecs) |
| Constellation | Leo |
| Discovery method | Transit |
| Discovery facility | K2 |
| Discovery year | 2016 |
Data: NASA Exoplanet Archive, last updated 2025-09-17. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About K2-27 b
Is K2-27 b habitable?
K2-27 b is not known to orbit within the habitable zone of K2-27, and as a Neptune-like planet it is an unlikely candidate for life as we know it.
How far away is K2-27 b?
K2-27 b is about 814 light-years from Earth in the constellation Leo. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 14,329,920 years to get there.
How big is K2-27 b compared to Earth?
K2-27 b has 4.74 times the radius of Earth and about 30.2 times its mass.
How long is a year on K2-27 b?
One orbit around K2-27 takes 6.8 Earth days — short enough that 54 of its years would fit into one Earth year.
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