K2-223 b
Astrophysical Synthesis & Habitability Characterization
K2-223 b is a confirmed sub-earth exoplanet orbiting the star K2-223, located approximately 647.8 light-years (198.6 parsecs) from the Solar System. First announced in 2018 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0048% across the stellar disk), this world measures 0.79 Earth radii and has a measured mass of 2.8 Earth masses. Combining its mass and radius yields a mean bulk density of 31.31 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 4.49 g⊕ (44.03 m/s²), and an escape velocity of 21.1 km/s.
In its orbital architecture around K2-223, K2-223 b completes one full revolution every 0.506 Earth days at a semi-major axis of 0.0135 AU (an ultra-close orbit less than one-seventh of Mercury's 0.387 AU distance from the Sun, where strong stellar tidal forces typically induce synchronous rotation). Its mean orbital velocity is approximately 290.5 km/s (compared to Earth's 29.8 km/s). The orbit is modeled as circular (e = 0.00), maintaining a constant stellar distance throughout its year.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 2480 K (+2207°C / +4005°F) and receiving 5,432.10 S⊕ (~7,393,086 W/m²), K2-223 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-223 is classified as a solar-type yellow star of spectral type G1 V with an effective photospheric temperature of 5,858 K, a radius of 1.05 R☉, a mass of 1.07 M☉, an estimated bolometric luminosity of 1.165 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.8 Gyr and a metallicity of [Fe/H] = 0.18 dex (metal-rich relative to the Sun). From Earth, K2-223 shines at apparent V-band magnitude 11.443 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The K2-223 system is a multi-planet architecture hosting 2 confirmed worlds, with K2-223 b sharing its stellar neighborhood alongside K2-223 c.
Methodology: Computed using the Schulze-Makuch et al. (2011) weighted metric comparing physical interior (radius, estimated density) and surface thermal regime (escape velocity, equilibrium temperature).
Discovery Facility: K2 · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | K2-223 |
| Spectral Type | G1 V |
| Effective Temp (Teff) | 5,858 K |
| Stellar Radius | 1.0500 R☉ |
| Stellar Mass | 1.0700 M☉ |
| Bolometric Luminosity | 1.165 L☉ |
| Metallicity [Fe/H] | 0.180 dex |
| Stellar Age | 2.800 Gyr |
| Apparent Magnitude | V: 11.443 · G: 11.274 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.013500 AU |
| Orbital Period | 0.506 days |
| Mean Orbital Velocity | 290.5 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 78.1000° |
| Mean Bulk Density | 31.31 g/cm³ (21.1 km/s vesc) |
| Insolation Flux | 5432.0988 S⊕ (~7,393,086 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 647.800 LY (198.604 pc) |