Kepler-717 b

Astrophysical Synthesis & Habitability Characterization

Kepler-717 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-717, located approximately 9150.2 light-years (2805.48 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0681% across the stellar disk), this world measures 2.42 Earth radii and has a measured mass of 6.44 Earth masses. Combining its mass and radius yields a mean bulk density of 2.51 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.1 g⊕ (10.79 m/s²), and an escape velocity of 18.2 km/s.

In its orbital architecture around Kepler-717, Kepler-717 b completes one full revolution every 4.408 Earth days at a semi-major axis of 0.052 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 128.3 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 1139 K (+866°C / +1591°F) and receiving 398.00 S⊕ (~541,678 W/m²), Kepler-717 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star Kepler-717 is classified as a stellar host with an effective photospheric temperature of 5,485 K, a radius of 0.85 R☉, a mass of 0.88 M☉, an estimated bolometric luminosity of 0.587 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.37 Gyr and a metallicity of [Fe/H] = -0.12 dex (metal-poor relative to the Sun). From Earth, Kepler-717 shines at apparent V-band magnitude 15.756 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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