K2-3 b
K2-3 b is a super-Earth orbiting the M V star K2-3 in the constellation Leo. It lies about 144 light-years from Earth and was discovered in 2015 using the transit method.
How Big Is K2-3 b?
K2-3 b has a radius of 2.08 times that of Earth. Its mass is 5.1 times that of Earth, giving it a density of 3.11 g/cm³ — between that of rocky and gaseous planets.
Is K2-3 b in the Habitable Zone?
K2-3 b orbits inside the inner edge of the habitable zone of K2-3. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of K2-3: 0.197–0.503 AU (conservative: 0.250–0.477 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
See the full interactive habitable-zone view in the Exoplanet Explorer app ›
Temperature on K2-3 b
The equilibrium temperature of K2-3 b is about 501 K (228 °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 10.50 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on K2-3 b — one full orbit around K2-3 — lasts 10.1 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.075 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.11).
How Was K2-3 b Discovered?
K2-3 b was discovered in 2015 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 K2-3 b?
K2-3 b is 143.7 light-years (44.1 parsecs) from Earth. Light arriving here tonight left the planet around the year 1883. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 2,529,120 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. K2-3 b scores 0.36, ranking #667 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: K2-3
K2-3
- Spectral type
- M V
- Surface temperature
- 3,844 K (Sun: 5,772 K)
- Mass
- 0.55 M☉
- Radius
- 0.55 R☉
- Luminosity
- 0.0587 L☉
- Age
- 6.9 billion years (Sun: 4.6)
The K2-3 Planetary System
K2-3 b is one of 3 known planets in the K2-3 system. Its siblings:
K2-3 b — Complete Data
| Radius | 2.078 Earth radii (0.185 Jupiter radii) |
|---|---|
| Mass | 5.11 Earth masses (0.016 Jupiter masses) |
| Density | 3.11 g/cm³ (Earth: 5.51) |
| Orbital period | 10.05 days |
| Orbital distance | 0.075 AU |
| Eccentricity | 0.107 |
| Equilibrium temperature | 501 K (228 °C) |
| Stellar irradiation | 10.50× Earth |
| Earth Similarity Index | 0.36 |
| Distance from Earth | 143.7 light-years (44.1 parsecs) |
| Constellation | Leo |
| Discovery method | Transit |
| Discovery facility | K2 |
| Discovery year | 2015 |
Data: NASA Exoplanet Archive, last updated 2023-07-10. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About K2-3 b
Is K2-3 b habitable?
No — K2-3 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is K2-3 b?
K2-3 b is about 144 light-years from Earth in the constellation Leo. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 2,529,120 years to get there.
How big is K2-3 b compared to Earth?
K2-3 b has 2.08 times the radius of Earth and about 5.1 times its mass.
How long is a year on K2-3 b?
One orbit around K2-3 takes 10.1 Earth days — short enough that 36 of its years would fit into one Earth year.
Explore K2-3 b in the app
Browse, filter and compare 6,000+ exoplanets on iPhone, iPad and Apple Watch — with habitable-zone views, widgets and offline data.
