Kepler-1798 b

Astrophysical Synthesis & Habitability Characterization

Kepler-1798 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-1798, located approximately 1289 light-years (395.2 parsecs) from the Solar System. First announced in 2021 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.1301% across the stellar disk), this world measures 2.309 Earth radii and has a measured mass of 5.94 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 1.11 g⊕ (10.89 m/s²), and an escape velocity of 17.9 km/s.

In its orbital architecture around Kepler-1798, Kepler-1798 b completes one full revolution every 16.856 Earth days at a semi-major axis of 0.1082 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 69.8 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 408 K (+135°C / +275°F) and receiving 6.52 S⊕ (~8,874 W/m²), Kepler-1798 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star Kepler-1798 is classified as a stellar host with an effective photospheric temperature of 3,967 K, a radius of 0.587 R☉, a mass of 0.593 M☉, an estimated bolometric luminosity of 0.077 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.36 Gyr and a metallicity of [Fe/H] = 0.06 dex (metal-rich relative to the Sun). From Earth, Kepler-1798 shines at apparent V-band magnitude 16.391 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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