Kepler-669 b

Astrophysical Synthesis & Habitability Characterization

Kepler-669 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-669, located approximately 6729.9 light-years (2063.41 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.1362% across the stellar disk), this world measures 4.83 Earth radii (0.43 Jupiter radii) and has a measured mass of 20.8 Earth masses. Combining its mass and radius yields a mean bulk density of 1.02 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.89 g⊕ (8.73 m/s²), and an escape velocity of 23.2 km/s.

In its orbital architecture around Kepler-669, Kepler-669 b completes one full revolution every 4.126 Earth days at a semi-major axis of 0.0529 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 139.5 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 1243 K (+970°C / +1778°F) and receiving 826.77 S⊕ (~1,125,227 W/m²), Kepler-669 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star Kepler-669 is classified as a stellar host with an effective photospheric temperature of 6,038 K, a radius of 1.2 R☉, a mass of 1.15 M☉, an estimated bolometric luminosity of 1.717 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.16 Gyr and a metallicity of [Fe/H] = 0.14 dex (metal-rich relative to the Sun). From Earth, Kepler-669 shines at apparent V-band magnitude 15.742 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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