Kepler-1840 b

Astrophysical Synthesis & Habitability Characterization

Kepler-1840 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-1840, located approximately 1673.5 light-years (513.11 parsecs) from the Solar System. First announced in 2021 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.1006% across the stellar disk), this world measures 2.778 Earth radii and has a measured mass of 8.13 Earth masses. Combining its mass and radius yields a mean bulk density of 2.09 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.05 g⊕ (10.3 m/s²), and an escape velocity of 19.1 km/s.

In its orbital architecture around Kepler-1840, Kepler-1840 b completes one full revolution every 131.19 Earth days at a semi-major axis of 0.46206 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 38.3 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 2.778 R⊕, Kepler-1840 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-1840 is classified as a stellar host with an effective photospheric temperature of 4,898 K, a radius of 0.803 R☉, a mass of 0.774 M☉, an estimated bolometric luminosity of 0.333 L☉. Stellar evolution modeling indicates an estimated stellar age of 14 Gyr and a metallicity of [Fe/H] = 0.14 dex (metal-rich relative to the Sun). From Earth, Kepler-1840 shines at apparent V-band magnitude 15.192 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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