Kepler-1021 b

Astrophysical Synthesis & Habitability Characterization

Kepler-1021 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-1021, located approximately 2642.1 light-years (810.08 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0617% across the stellar disk), this world measures 2.33 Earth radii and has a measured mass of 6.04 Earth masses. Combining its mass and radius yields a mean bulk density of 2.63 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.11 g⊕ (10.89 m/s²), and an escape velocity of 18 km/s.

In its orbital architecture around Kepler-1021, Kepler-1021 b completes one full revolution every 13.475 Earth days at a semi-major axis of 0.1034 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 83.5 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 634 K (+361°C / +682°F) and receiving 50.37 S⊕ (~68,554 W/m²), Kepler-1021 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star Kepler-1021 is classified as a stellar host with an effective photospheric temperature of 5,431 K, a radius of 0.86 R☉, a mass of 0.89 M☉, an estimated bolometric luminosity of 0.577 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.68 Gyr and a metallicity of [Fe/H] = -0.05 dex (near-solar heavy-element abundance). From Earth, Kepler-1021 shines at apparent V-band magnitude 15.207 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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