Kepler-855 b

Astrophysical Synthesis & Habitability Characterization

Kepler-855 b is a confirmed gas giant exoplanet orbiting the star Kepler-855, located approximately 4913.8 light-years (1506.58 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.5524% across the stellar disk), this world measures 8.35 Earth radii (0.74 Jupiter radii) and has a measured mass of 52.7 Earth masses (0.17 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.5 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.76 g⊕ (7.45 m/s²), and an escape velocity of 28.1 km/s.

In its orbital architecture around Kepler-855, Kepler-855 b completes one full revolution every 7.887 Earth days at a semi-major axis of 0.0762 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 105.1 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 996 K (+723°C / +1333°F) and receiving 405.18 S⊕ (~551,454 W/m²), Kepler-855 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star Kepler-855 is classified as a stellar host with an effective photospheric temperature of 5,835 K, a radius of 1.03 R☉, a mass of 1.03 M☉, an estimated bolometric luminosity of 1.103 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.17 Gyr and a metallicity of [Fe/H] = 0.06 dex (metal-rich relative to the Sun). From Earth, Kepler-855 shines at apparent V-band magnitude 15.157 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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