Kepler-1621 b

Astrophysical Synthesis & Habitability Characterization

Kepler-1621 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-1621, located approximately 5321.8 light-years (1631.66 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0255% across the stellar disk), this world measures 2.16 Earth radii and has a measured mass of 5.31 Earth masses. Combining its mass and radius yields a mean bulk density of 2.91 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.14 g⊕ (11.18 m/s²), and an escape velocity of 17.5 km/s.

In its orbital architecture around Kepler-1621, Kepler-1621 b completes one full revolution every 92.264 Earth days at a semi-major axis of 0.4204 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 49.6 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 469 K (+196°C / +385°F) and receiving 14.06 S⊕ (~19,129 W/m²), Kepler-1621 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star Kepler-1621 is classified as a stellar host with an effective photospheric temperature of 6,158 K, a radius of 1.24 R☉, a mass of 1.15 M☉, an estimated bolometric luminosity of 1.984 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.69 Gyr and a metallicity of [Fe/H] = 0.03 dex (near-solar heavy-element abundance). From Earth, Kepler-1621 shines at apparent V-band magnitude 15.151 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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