Kepler-661 b

Astrophysical Synthesis & Habitability Characterization

Kepler-661 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-661, located approximately 1744.2 light-years (534.79 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.1765% across the stellar disk), this world measures 3.07 Earth radii (0.27 Jupiter radii) and has a measured mass of 9.64 Earth masses. Combining its mass and radius yields a mean bulk density of 1.84 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.02 g⊕ (10 m/s²), and an escape velocity of 19.8 km/s.

In its orbital architecture around Kepler-661, Kepler-661 b completes one full revolution every 6.029 Earth days at a semi-major axis of 0.0585 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 105.6 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 678 K (+405°C / +761°F) and receiving 45.53 S⊕ (~61,964 W/m²), Kepler-661 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star Kepler-661 is classified as a stellar host with an effective photospheric temperature of 4,483 K, a radius of 0.67 R☉, a mass of 0.7 M☉, an estimated bolometric luminosity of 0.163 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.27 Gyr and a metallicity of [Fe/H] = -0.05 dex (near-solar heavy-element abundance). From Earth, Kepler-661 shines at apparent V-band magnitude 16.016 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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