Kepler-877 b

Astrophysical Synthesis & Habitability Characterization

Kepler-877 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-877, located approximately 1964 light-years (602.18 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0576% across the stellar disk), this world measures 2.12 Earth radii and has a measured mass of 5.14 Earth masses. Combining its mass and radius yields a mean bulk density of 2.97 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.14 g⊕ (11.18 m/s²), and an escape velocity of 17.4 km/s.

In its orbital architecture around Kepler-877, Kepler-877 b completes one full revolution every 18.458 Earth days at a semi-major axis of 0.1301 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 76.7 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 632 K (+359°C / +678°F) and receiving 37.81 S⊕ (~51,459 W/m²), Kepler-877 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star Kepler-877 is classified as a stellar host with an effective photospheric temperature of 5,261 K, a radius of 0.81 R☉, a mass of 0.85 M☉, an estimated bolometric luminosity of 0.451 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.57 Gyr and a metallicity of [Fe/H] = -0.06 dex (near-solar heavy-element abundance). From Earth, Kepler-877 shines at apparent V-band magnitude 14.74 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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