K2-22 b
Astrophysical Synthesis & Habitability Characterization
K2-22 b is a confirmed sub-neptune exoplanet orbiting the star K2-22, located approximately 795.3 light-years (243.84 parsecs) from the Solar System. First announced in 2015 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.1322% across the stellar disk), this world measures 2.3 Earth radii and has a measured mass of 444.962 Earth masses (1.4 Jupiter masses). Combining its mass and radius yields a mean bulk density of 201.65 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 84.11 g⊕ (824.84 m/s²), and an escape velocity of 155.6 km/s.
In its orbital architecture around K2-22, K2-22 b completes one full revolution every 0.381 Earth days at a semi-major axis of 0.009 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 256.9 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.19 carries the world between 0.0073 AU at periapsis and 0.0107 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 2100 K (+1827°C / +3321°F) and receiving 114.00 S⊕ (~155,154 W/m²), K2-22 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-22 is classified as a low-mass red dwarf of spectral type M0 V with an effective photospheric temperature of 3,879 K, a radius of 0.58 R☉, a mass of 0.5953 M☉, an estimated bolometric luminosity of 0.068 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.032 dex (near-solar heavy-element abundance). From Earth, K2-22 shines at apparent V-band magnitude 15.565 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.
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 | K2-22 |
| Spectral Type | M0 V |
| Effective Temp (Teff) | 3,879 K |
| Stellar Radius | 0.5800 R☉ |
| Stellar Mass | 0.5953 M☉ |
| Bolometric Luminosity | 0.068 L☉ |
| Metallicity [Fe/H] | 0.032 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 15.565 · G: 14.954 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.009000 AU |
| Orbital Period | 0.381 days |
| Mean Orbital Velocity | 256.9 km/s |
| Orbital Eccentricity (e) | 0.19000 |
| Orbital Inclination (i) | 90.6000° |
| Mean Bulk Density | 201.65 g/cm³ (155.6 km/s vesc) |
| Insolation Flux | 114.0000 S⊕ (~155,154 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 795.300 LY (243.836 pc) |