Kepler-677 b

Astrophysical Synthesis & Habitability Characterization

Kepler-677 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-677, located approximately 6373.3 light-years (1954.08 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.2482% across the stellar disk), this world measures 5.38 Earth radii (0.48 Jupiter radii) and has a measured mass of 25 Earth masses. Combining its mass and radius yields a mean bulk density of 0.89 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.86 g⊕ (8.43 m/s²), and an escape velocity of 24.1 km/s.

In its orbital architecture around Kepler-677, Kepler-677 b completes one full revolution every 6.575 Earth days at a semi-major axis of 0.067 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 110.9 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 1015 K (+742°C / +1368°F) and receiving 683.27 S⊕ (~929,936 W/m²), Kepler-677 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star Kepler-677 is classified as a stellar host with an effective photospheric temperature of 5,723 K, a radius of 0.99 R☉, a mass of 1 M☉, an estimated bolometric luminosity of 0.943 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.57 Gyr and a metallicity of [Fe/H] = 0.06 dex (metal-rich relative to the Sun). From Earth, Kepler-677 shines at apparent V-band magnitude 15.504 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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