K2-223 b
K2-223 b is a lava world orbiting the G1 V star K2-223 in the constellation Virgo. It lies about 648 light-years from Earth and was discovered in 2018 using the transit method.
How Big Is K2-223 b?
K2-223 b has a radius of 0.79 times that of Earth. Its mass is 2.8 times that of Earth, giving it a density of 31.43 g/cm³ — comparable to rocky planets like Earth (5.51 g/cm³).
Is K2-223 b in the Habitable Zone?
K2-223 b orbits inside the inner edge of the habitable zone of K2-223. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of K2-223: 0.743–1.747 AU (conservative: 0.941–1.656 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on K2-223 b
The equilibrium temperature of K2-223 b is about 2,480 K (2,207 °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 K2-223 b — one full orbit around K2-223 — lasts just 12.1 hours, shorter than Mercury's 88-day year. It orbits at an average distance of 0.014 AU — closer to its star than Mercury is to the Sun.
How Was K2-223 b Discovered?
K2-223 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 K2-223 b?
K2-223 b is 647.8 light-years (198.6 parsecs) from Earth. Light arriving here tonight left the planet around the year 1379. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 11,401,280 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. K2-223 b scores 0.29, ranking #1,744 of 5,565 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: K2-223
K2-223
- Spectral type
- G1 V
- Surface temperature
- 5,858 K (Sun: 5,772 K)
- Mass
- 1.07 M☉
- Radius
- 1.05 R☉
- Luminosity
- 0.9900 L☉
- Age
- 2.8 billion years (Sun: 4.6)
The K2-223 Planetary System
K2-223 b is one of 2 known planets in the K2-223 system. Its siblings:
- K2-223 c (Super Earth)
K2-223 b — Complete Data
| Radius | 0.790 Earth radii (0.070 Jupiter radii) |
|---|---|
| Mass | 2.80 Earth masses (0.009 Jupiter masses) |
| Density | 31.43 g/cm³ (Earth: 5.51) |
| Orbital period | 0.51 days |
| Orbital distance | 0.014 AU |
| Equilibrium temperature | 2,480 K (2,207 °C) |
| Earth Similarity Index | 0.29 |
| Distance from Earth | 647.8 light-years (198.6 parsecs) |
| Constellation | Virgo |
| Discovery method | Transit |
| Discovery facility | K2 |
| Discovery year | 2018 |
Data: NASA Exoplanet Archive, last updated 2026-09-25. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About K2-223 b
Is K2-223 b habitable?
No — K2-223 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is K2-223 b?
K2-223 b is about 648 light-years from Earth in the constellation Virgo. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 11,401,280 years to get there.
How big is K2-223 b compared to Earth?
K2-223 b has 0.79 times the radius of Earth and about 2.8 times its mass.
How long is a year on K2-223 b?
One orbit around K2-223 takes 0.5 Earth days — short enough that 722 of its years would fit into one Earth year.
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