K2-85 b

Astrophysical Synthesis & Habitability Characterization

K2-85 b is a confirmed super-earth exoplanet orbiting the star K2-85, located approximately 317.1 light-years (97.22 parsecs) from the Solar System. First announced in 2016 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0327% across the stellar disk), this world measures 1.4 Earth radii and has a measured mass of 3.2 Earth masses. Combining its mass and radius yields a mean bulk density of 6.43 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.63 g⊕ (15.98 m/s²), and an escape velocity of 16.9 km/s.

In its orbital architecture around K2-85, K2-85 b completes one full revolution every 0.685 Earth days at a semi-major axis of 0.013 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 206.6 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.24 carries the world between 0.0099 AU at periapsis and 0.0161 AU at apoapsis, driving measurable seasonal insolation cycles.

⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1355 K (+1082°C / +1980°F) and receiving 800.00 S⊕ (~1,088,800 W/m²), K2-85 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star K2-85 is classified as a stellar host with an effective photospheric temperature of 4,232 K, a radius of 0.71 R☉, a mass of 0.7 M☉, an estimated bolometric luminosity of 0.145 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.14 dex (metal-rich relative to the Sun). From Earth, K2-85 shines at apparent V-band magnitude 12.416 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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