Kepler-1121 b

Astrophysical Synthesis & Habitability Characterization

Kepler-1121 b is a confirmed super-earth exoplanet orbiting the star Kepler-1121, located approximately 1572.2 light-years (482.05 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0121% across the stellar disk), this world measures 1.91 Earth radii and has a measured mass of 4.31 Earth masses. Combining its mass and radius yields a mean bulk density of 3.41 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.18 g⊕ (11.57 m/s²), and an escape velocity of 16.8 km/s.

In its orbital architecture around Kepler-1121, Kepler-1121 b completes one full revolution every 13.151 Earth days at a semi-major axis of 0.11818 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 97.8 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 1008 K (+735°C / +1355°F) and receiving 205.27 S⊕ (~279,375 W/m²), Kepler-1121 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star Kepler-1121 is classified as a stellar host with an effective photospheric temperature of 6,231 K, a radius of 1.59 R☉, a mass of 1.29 M☉, an estimated bolometric luminosity of 3.419 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.02 Gyr and a metallicity of [Fe/H] = 0.12 dex (metal-rich relative to the Sun). From Earth, Kepler-1121 shines at apparent V-band magnitude 12.144 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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