K2-216 b

Astrophysical Synthesis & Habitability Characterization

K2-216 b is a confirmed super-earth exoplanet orbiting the star K2-216, located approximately 376.6 light-years (115.46 parsecs) from the Solar System. First announced in 2018 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0497% across the stellar disk), this world measures 1.75 Earth radii and has a measured mass of 8 Earth masses. Combining its mass and radius yields a mean bulk density of 8.23 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 2.61 g⊕ (25.6 m/s²), and an escape velocity of 23.9 km/s.

In its orbital architecture around K2-216, K2-216 b completes one full revolution every 2.175 Earth days at a semi-major axis of 0.028 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 140.1 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 1103 K (+830°C / +1526°F) and receiving 248.00 S⊕ (~337,528 W/m²), K2-216 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star K2-216 is classified as an orange K-type star of spectral type K5 V with an effective photospheric temperature of 4,503 K, a radius of 0.72 R☉, a mass of 0.7 M☉, an estimated bolometric luminosity of 0.191 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0 dex (near-solar heavy-element abundance). From Earth, K2-216 shines at apparent V-band magnitude 12.403 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

Discovery Facility: K2 · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).