Kepler-1738 b

Astrophysical Synthesis & Habitability Characterization

Kepler-1738 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-1738, located approximately 4249.4 light-years (1302.87 parsecs) from the Solar System. First announced in 2021 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0669% across the stellar disk), this world measures 2.825 Earth radii and has a measured mass of 8.37 Earth masses. Combining its mass and radius yields a mean bulk density of 2.05 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 19.3 km/s.

In its orbital architecture around Kepler-1738, Kepler-1738 b completes one full revolution every 7.675 Earth days at a semi-major axis of 0.0781 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 110.7 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 957 K (+684°C / +1263°F) and receiving 198.67 S⊕ (~270,390 W/m²), Kepler-1738 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star Kepler-1738 is classified as a stellar host with an effective photospheric temperature of 6,063 K, a radius of 1.001 R☉, a mass of 1.079 M☉, an estimated bolometric luminosity of 1.215 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.3 Gyr and a metallicity of [Fe/H] = -0.02 dex (near-solar heavy-element abundance). From Earth, Kepler-1738 shines at apparent V-band magnitude 15.649 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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