Kepler-1939 b

Astrophysical Synthesis & Habitability Characterization

Kepler-1939 b is a confirmed terrestrial exoplanet orbiting the star Kepler-1939, located approximately 619.2 light-years (189.83 parsecs) from the Solar System. First announced in 2021 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0314% across the stellar disk), this world measures 1.165 Earth radii and has a measured mass of 1.68 Earth masses. Combining its mass and radius yields a mean bulk density of 5.86 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.24 g⊕ (12.16 m/s²), and an escape velocity of 13.4 km/s.

In its orbital architecture around Kepler-1939, Kepler-1939 b completes one full revolution every 2.791 Earth days at a semi-major axis of 0.0334 AU (an ultra-close orbit less than one-seventh of Mercury's 0.387 AU distance from the Sun, where strong stellar tidal forces typically induce synchronous rotation). 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 816 K (+543°C / +1009°F) and receiving 104.74 S⊕ (~142,551 W/m²), Kepler-1939 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star Kepler-1939 is classified as a stellar host with an effective photospheric temperature of 4,353 K, a radius of 0.603 R☉, a mass of 0.648 M☉, an estimated bolometric luminosity of 0.117 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.18 dex (metal-poor relative to the Sun). From Earth, Kepler-1939 shines at apparent V-band magnitude 13.622 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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