K2-115 b
K2-115 b is a cold gas giant orbiting K2-115 in the constellation Cancer. It lies about 1,349 light-years from Earth and was discovered in 2017 using the transit method.
How Big Is K2-115 b?
K2-115 b has a radius of 11.80 times that of Earth, or 1.05 times the radius of Jupiter. Its mass is 321 times that of Earth, giving it a density of 1.07 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is K2-115 b in the Habitable Zone?
K2-115 b orbits inside the inner edge of the habitable zone of K2-115. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of K2-115: 0.659–1.549 AU (conservative: 0.835–1.469 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on K2-115 b
The equilibrium temperature of K2-115 b is about 696 K (423 °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.
Orbit and Year Length
A year on K2-115 b — one full orbit around K2-115 — lasts 20.3 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.142 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.06).
How Was K2-115 b Discovered?
K2-115 b was discovered in 2017 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 K2-115 b?
K2-115 b is 1,349.0 light-years (413.6 parsecs) from Earth. Light arriving here tonight left the planet about 1,349 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 23,742,400 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. K2-115 b scores 0.10, ranking #4,421 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: K2-115
K2-115
- Surface temperature
- 5,870 K (Sun: 5,772 K)
- Mass
- 0.92 M☉
- Radius
- 0.86 R☉
- Luminosity
- 0.7800 L☉
- Age
- 2.2 billion years (Sun: 4.6)
Planetary System
K2-115 b is the only planet known to orbit K2-115 so far.
K2-115 b — Complete Data
| Radius | 11.803 Earth radii (1.053 Jupiter radii) |
|---|---|
| Mass | 321.01 Earth masses (1.010 Jupiter masses) |
| Density | 1.07 g/cm³ (Earth: 5.51) |
| Orbital period | 20.27 days |
| Orbital distance | 0.142 AU |
| Eccentricity | 0.063 |
| Equilibrium temperature | 696 K (423 °C) |
| Earth Similarity Index | 0.10 |
| Distance from Earth | 1,349.0 light-years (413.6 parsecs) |
| Constellation | Cancer |
| Discovery method | Transit |
| Discovery facility | K2 |
| Discovery year | 2017 |
Data: NASA Exoplanet Archive, last updated 2024-11-20. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About K2-115 b
Is K2-115 b habitable?
No — K2-115 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is K2-115 b?
K2-115 b is about 1,349 light-years from Earth in the constellation Cancer. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 23,742,400 years to get there.
How big is K2-115 b compared to Earth?
K2-115 b has 11.80 times the radius of Earth and about 321 times its mass.
How long is a year on K2-115 b?
One orbit around K2-115 takes 20.3 Earth days — short enough that 18 of its years would fit into one Earth year.
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