Kepler-809 b

Astrophysical Synthesis & Habitability Characterization

Kepler-809 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-809, located approximately 3135.7 light-years (961.41 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0793% across the stellar disk), this world measures 3.01 Earth radii (0.27 Jupiter radii) and has a measured mass of 9.32 Earth masses. Combining its mass and radius yields a mean bulk density of 1.88 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.03 g⊕ (10.1 m/s²), and an escape velocity of 19.7 km/s.

In its orbital architecture around Kepler-809, Kepler-809 b completes one full revolution every 55.639 Earth days at a semi-major axis of 0.2901 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 56.7 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 478 K (+205°C / +401°F) and receiving 13.16 S⊕ (~17,904 W/m²), Kepler-809 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star Kepler-809 is classified as a stellar host with an effective photospheric temperature of 5,734 K, a radius of 0.98 R☉, a mass of 0.99 M☉, an estimated bolometric luminosity of 0.931 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.37 Gyr and a metallicity of [Fe/H] = 0.04 dex (near-solar heavy-element abundance). From Earth, Kepler-809 shines at apparent V-band magnitude 14.875 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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