Kepler-666 b

Astrophysical Synthesis & Habitability Characterization

Kepler-666 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-666, located approximately 4920.7 light-years (1508.71 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0439% across the stellar disk), this world measures 2.4 Earth radii and has a measured mass of 6.35 Earth masses. Combining its mass and radius yields a mean bulk density of 2.53 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.1 g⊕ (10.79 m/s²), and an escape velocity of 18.2 km/s.

In its orbital architecture around Kepler-666, Kepler-666 b completes one full revolution every 4.499 Earth days at a semi-major axis of 0.0542 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 131.1 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 1133 K (+860°C / +1580°F) and receiving 575.64 S⊕ (~783,451 W/m²), Kepler-666 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star Kepler-666 is classified as a stellar host with an effective photospheric temperature of 5,887 K, a radius of 1.05 R☉, a mass of 1.03 M☉, an estimated bolometric luminosity of 1.188 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.8 Gyr and a metallicity of [Fe/H] = 0.01 dex (near-solar heavy-element abundance). From Earth, Kepler-666 shines at apparent V-band magnitude 15.422 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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