Kepler-739 b

Astrophysical Synthesis & Habitability Characterization

Kepler-739 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-739, located approximately 4470.5 light-years (1370.65 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.1144% across the stellar disk), this world measures 3.32 Earth radii (0.3 Jupiter radii) and has a measured mass of 11 Earth masses. Combining its mass and radius yields a mean bulk density of 1.66 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1 g⊕ (9.81 m/s²), and an escape velocity of 20.4 km/s.

In its orbital architecture around Kepler-739, Kepler-739 b completes one full revolution every 12.532 Earth days at a semi-major axis of 0.1054 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 91.5 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 775 K (+502°C / +936°F) and receiving 115.96 S⊕ (~157,826 W/m²), Kepler-739 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star Kepler-739 is classified as a stellar host with an effective photospheric temperature of 5,601 K, a radius of 0.9 R☉, a mass of 0.93 M☉, an estimated bolometric luminosity of 0.715 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.27 Gyr and a metallicity of [Fe/H] = -0.08 dex (near-solar heavy-element abundance). From Earth, Kepler-739 shines at apparent V-band magnitude 15.711 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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