Kepler-868 b

Astrophysical Synthesis & Habitability Characterization

Kepler-868 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-868, located approximately 5196.1 light-years (1593.13 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0446% across the stellar disk), this world measures 2.05 Earth radii and has a measured mass of 4.86 Earth masses. Combining its mass and radius yields a mean bulk density of 3.11 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.16 g⊕ (11.38 m/s²), and an escape velocity of 17.2 km/s.

In its orbital architecture around Kepler-868, Kepler-868 b completes one full revolution every 5.033 Earth days at a semi-major axis of 0.0575 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 124.3 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 1047 K (+774°C / +1425°F) and receiving 417.03 S⊕ (~567,583 W/m²), Kepler-868 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star Kepler-868 is classified as a stellar host with an effective photospheric temperature of 5,614 K, a radius of 0.89 R☉, a mass of 0.93 M☉, an estimated bolometric luminosity of 0.706 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.89 Gyr and a metallicity of [Fe/H] = -0.08 dex (near-solar heavy-element abundance). From Earth, Kepler-868 shines at apparent V-band magnitude 15.872 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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