Kepler-477 b

Astrophysical Synthesis & Habitability Characterization

Kepler-477 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-477, located approximately 1197 light-years (367 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0577% across the stellar disk), this world measures 2.07 Earth radii and has a measured mass of 4.94 Earth masses. Combining its mass and radius yields a mean bulk density of 3.07 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.15 g⊕ (11.28 m/s²), and an escape velocity of 17.3 km/s.

In its orbital architecture around Kepler-477, Kepler-477 b completes one full revolution every 11.12 Earth days at a semi-major axis of 0.0911 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 89.1 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 649 K (+376°C / +709°F) and receiving 38.71 S⊕ (~52,684 W/m²), Kepler-477 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star Kepler-477 is classified as a stellar host with an effective photospheric temperature of 5,240 K, a radius of 0.79 R☉, a mass of 0.87 M☉, an estimated bolometric luminosity of 0.422 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.09 Gyr and a metallicity of [Fe/H] = -0.04 dex (near-solar heavy-element abundance). From Earth, Kepler-477 shines at apparent V-band magnitude 13.835 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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