Kepler-1881 b

Astrophysical Synthesis & Habitability Characterization

Kepler-1881 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-1881, located approximately 3448.2 light-years (1057.21 parsecs) from the Solar System. First announced in 2021 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0978% across the stellar disk), this world measures 2.981 Earth radii and has a measured mass of 9.17 Earth masses. Combining its mass and radius yields a mean bulk density of 1.91 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.03 g⊕ (10.1 m/s²), and an escape velocity of 19.6 km/s.

In its orbital architecture around Kepler-1881, Kepler-1881 b completes one full revolution every 159.394 Earth days at a semi-major axis of 0.53325 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 36.4 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.

☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 2.981 R⊕, Kepler-1881 b exceeds the empirical ~1.8–2.2 R⊕ Fulton radius valley threshold, indicating a substantial hydrogen-helium or supercritical volatile envelope without a conventional solid terrestrial surface.

The host star Kepler-1881 is classified as a stellar host with an effective photospheric temperature of 5,135 K, a radius of 0.874 R☉, a mass of 0.812 M☉, an estimated bolometric luminosity of 0.477 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.9 Gyr and a metallicity of [Fe/H] = 0.12 dex (metal-rich relative to the Sun). From Earth, Kepler-1881 shines at apparent V-band magnitude 15.898 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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