Kepler-1668 b

Astrophysical Synthesis & Habitability Characterization

Kepler-1668 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-1668, located approximately 4356.3 light-years (1335.64 parsecs) from the Solar System. First announced in 2020 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.1535% across the stellar disk), this world measures 4.348 Earth radii (0.39 Jupiter radii) and has a measured mass of 17.4 Earth masses. Combining its mass and radius yields a mean bulk density of 1.17 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.92 g⊕ (9.02 m/s²), and an escape velocity of 22.4 km/s.

In its orbital architecture around Kepler-1668, Kepler-1668 b completes one full revolution every 15.434 Earth days at a semi-major axis of 0.124 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 87.4 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 721 K (+448°C / +838°F) and receiving 63.79 S⊕ (~86,818 W/m²), Kepler-1668 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star Kepler-1668 is classified as a stellar host with an effective photospheric temperature of 5,542 K, a radius of 1.0174 R☉, a mass of 0.98 M☉, an estimated bolometric luminosity of 0.876 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.07 dex (metal-rich relative to the Sun). From Earth, Kepler-1668 shines at apparent V-band magnitude 15.792 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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