Kepler-1730 b

Astrophysical Synthesis & Habitability Characterization

Kepler-1730 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-1730, located approximately 4654.5 light-years (1427.08 parsecs) from the Solar System. First announced in 2021 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.1296% across the stellar disk), this world measures 4.485 Earth radii (0.4 Jupiter radii) and has a measured mass of 18.4 Earth masses. Combining its mass and radius yields a mean bulk density of 1.12 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.91 g⊕ (8.92 m/s²), and an escape velocity of 22.7 km/s.

In its orbital architecture around Kepler-1730, Kepler-1730 b completes one full revolution every 13.81 Earth days at a semi-major axis of 0.1131 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 89.1 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 833 K (+560°C / +1040°F) and receiving 113.75 S⊕ (~154,814 W/m²), Kepler-1730 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star Kepler-1730 is classified as a stellar host with an effective photospheric temperature of 5,942 K, a radius of 1.142 R☉, a mass of 1.009 M☉, an estimated bolometric luminosity of 1.459 L☉. Stellar evolution modeling indicates an estimated stellar age of 7.4 Gyr and a metallicity of [Fe/H] = -0.04 dex (near-solar heavy-element abundance). From Earth, Kepler-1730 shines at apparent V-band magnitude 15.478 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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