K2-212 b
Astrophysical Synthesis & Habitability Characterization
K2-212 b is a confirmed sub-neptune exoplanet orbiting the star K2-212, located approximately 356.2 light-years (109.22 parsecs) from the Solar System. First announced in 2018 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.1284% across the stellar disk), this world measures 2.65 Earth radii and has a measured mass of 7.51 Earth masses. Combining its mass and radius yields a mean bulk density of 2.23 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.07 g⊕ (10.49 m/s²), and an escape velocity of 18.8 km/s.
In its orbital architecture around K2-212, K2-212 b completes one full revolution every 9.796 Earth days at a semi-major axis of 0.0785 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 87.2 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 542 K (+269°C / +516°F) and receiving 21.96 S⊕ (~29,893 W/m²), K2-212 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-212 is classified as a stellar host with an effective photospheric temperature of 4,349 K, a radius of 0.678 R☉, a mass of 0.622 M☉, an estimated bolometric luminosity of 0.148 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.03 dex (near-solar heavy-element abundance). From Earth, K2-212 shines at apparent V-band magnitude 12.977 (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 | K2-212 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 4,349 K |
| Stellar Radius | 0.6780 R☉ |
| Stellar Mass | 0.6220 M☉ |
| Bolometric Luminosity | 0.148 L☉ |
| Metallicity [Fe/H] | 0.030 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 12.977 · G: 12.550 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.078500 AU |
| Orbital Period | 9.796 days |
| Mean Orbital Velocity | 87.2 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 89.1915° |
| Mean Bulk Density | 2.23 g/cm³ (18.8 km/s vesc) |
| Insolation Flux | 21.9640 S⊕ (~29,893 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 356.200 LY (109.218 pc) |