Kepler-981 b

Astrophysical Synthesis & Habitability Characterization

Kepler-981 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-981, located approximately 2863.9 light-years (878.08 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0487% across the stellar disk), this world measures 2.31 Earth radii and has a measured mass of 5.95 Earth masses. Combining its mass and radius yields a mean bulk density of 2.66 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.12 g⊕ (10.98 m/s²), and an escape velocity of 18 km/s.

In its orbital architecture around Kepler-981, Kepler-981 b completes one full revolution every 4.47 Earth days at a semi-major axis of 0.0535 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 130.2 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 1103 K (+830°C / +1526°F) and receiving 337.47 S⊕ (~459,298 W/m²), Kepler-981 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star Kepler-981 is classified as a stellar host with an effective photospheric temperature of 5,718 K, a radius of 0.96 R☉, a mass of 0.98 M☉, an estimated bolometric luminosity of 0.884 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.07 Gyr and a metallicity of [Fe/H] = 0.01 dex (near-solar heavy-element abundance). From Earth, Kepler-981 shines at apparent V-band magnitude 14.875 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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