K2-329 b

Astrophysical Synthesis & Habitability Characterization

K2-329 b is a confirmed gas giant exoplanet orbiting the star K2-329, located approximately 760.7 light-years (233.24 parsecs) from the Solar System. First announced in 2020 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.9363% across the stellar disk), this world measures 8.676 Earth radii (0.77 Jupiter radii) and has a measured mass of 82.636 Earth masses (0.26 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.7 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.1 g⊕ (10.79 m/s²), and an escape velocity of 34.5 km/s.

In its orbital architecture around K2-329, K2-329 b completes one full revolution every 12.455 Earth days at a semi-major axis of 0.1016 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 88.7 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.0697 carries the world between 0.0945 AU at periapsis and 0.1087 AU at apoapsis, driving measurable seasonal insolation cycles.

⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 650 K (+377°C / +711°F) and receiving 45.70 S⊕ (~62,198 W/m²), K2-329 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star K2-329 is classified as a stellar host with an effective photospheric temperature of 5,282 K, a radius of 0.822 R☉, a mass of 0.901 M☉, an estimated bolometric luminosity of 0.472 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.8 Gyr and a metallicity of [Fe/H] = 0.098 dex (metal-rich relative to the Sun). From Earth, K2-329 shines at apparent V-band magnitude 12.697 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere.

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