K2-211 b
Astrophysical Synthesis & Habitability Characterization
K2-211 b is a confirmed super-earth exoplanet orbiting the star K2-211, located approximately 888.1 light-years (272.3 parsecs) from the Solar System. First announced in 2018 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0223% across the stellar disk), this world measures 1.332 Earth radii and has a measured mass of 2.33 Earth masses. Combining its mass and radius yields a mean bulk density of 5.44 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.31 g⊕ (12.85 m/s²), and an escape velocity of 14.8 km/s.
In its orbital architecture around K2-211, K2-211 b completes one full revolution every 0.67 Earth days at a semi-major axis of 0.01419 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 230.6 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.19 carries the world between 0.0115 AU at periapsis and 0.0169 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1873 K (+1600°C / +2912°F) and receiving 2,056.06 S⊕ (~2,798,296 W/m²), K2-211 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-211 is classified as a stellar host with an effective photospheric temperature of 5,117 K, a radius of 0.818 R☉, a mass of 0.851 M☉, an estimated bolometric luminosity of 0.412 L☉. Stellar evolution modeling indicates an estimated stellar age of 6.5 Gyr and a metallicity of [Fe/H] = 0.134 dex (metal-rich relative to the Sun). From Earth, K2-211 shines at apparent V-band magnitude 13.155 (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 | K2-211 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,117 K |
| Stellar Radius | 0.8180 R☉ |
| Stellar Mass | 0.8510 M☉ |
| Bolometric Luminosity | 0.412 L☉ |
| Metallicity [Fe/H] | 0.134 dex |
| Stellar Age | 6.500 Gyr |
| Apparent Magnitude | V: 13.155 · G: 12.933 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.014190 AU |
| Orbital Period | 0.67 days |
| Mean Orbital Velocity | 230.6 km/s |
| Orbital Eccentricity (e) | 0.19000 |
| Orbital Inclination (i) | 84.1000° |
| Mean Bulk Density | 5.44 g/cm³ (14.8 km/s vesc) |
| Insolation Flux | 2056.0589 S⊕ (~2,798,296 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 888.100 LY (272.297 pc) |