K2-79 b

Astrophysical Synthesis & Habitability Characterization

K2-79 b is a confirmed sub-neptune exoplanet orbiting the star K2-79, located approximately 835 light-years (256.01 parsecs) from the Solar System. First announced in 2016 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0899% across the stellar disk), this world measures 4.15 Earth radii (0.37 Jupiter radii) and has a measured mass of 5.9 Earth masses. Combining its mass and radius yields a mean bulk density of 0.46 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.34 g⊕ (3.33 m/s²), and an escape velocity of 13.3 km/s.

In its orbital architecture around K2-79, K2-79 b completes one full revolution every 10.995 Earth days at a semi-major axis of 0.0987 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 97.7 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.032 (ranging from 0.0955 AU at periapsis to 0.1019 AU at apoapsis), the planet experiences minimal orbital distance variation.

⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1033 K (+760°C / +1400°F) and receiving 180.00 S⊕ (~244,980 W/m²), K2-79 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star K2-79 is classified as a solar-type yellow star of spectral type G1 with an effective photospheric temperature of 5,897 K, a radius of 1.269 R☉, a mass of 1.06 M☉, an estimated bolometric luminosity of 1.747 L☉. Stellar evolution modeling indicates an estimated stellar age of 6.5 Gyr and a metallicity of [Fe/H] = 0.035 dex (near-solar heavy-element abundance). From Earth, K2-79 shines at apparent V-band magnitude 12.152 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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