Kepler-1720 b

Astrophysical Synthesis & Habitability Characterization

Kepler-1720 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-1720, located approximately 2053 light-years (629.45 parsecs) from the Solar System. First announced in 2021 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.1235% across the stellar disk), this world measures 3.216 Earth radii (0.29 Jupiter radii) and has a measured mass of 10.4 Earth masses. Combining its mass and radius yields a mean bulk density of 1.72 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.01 g⊕ (9.9 m/s²), and an escape velocity of 20.1 km/s.

In its orbital architecture around Kepler-1720, Kepler-1720 b completes one full revolution every 12.706 Earth days at a semi-major axis of 0.1043 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 89.3 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.

⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 697 K (+424°C / +795°F) and receiving 55.86 S⊕ (~76,025 W/m²), Kepler-1720 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star Kepler-1720 is classified as a stellar host with an effective photospheric temperature of 5,573 K, a radius of 0.839 R☉, a mass of 0.939 M☉, an estimated bolometric luminosity of 0.609 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.5 Gyr and a metallicity of [Fe/H] = -0.04 dex (near-solar heavy-element abundance). From Earth, Kepler-1720 shines at apparent V-band magnitude 14.822 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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