KOI-217 b

Astrophysical Synthesis & Habitability Characterization

KOI-217 b is a confirmed gas giant exoplanet orbiting the star KOI-217, located approximately 2983.3 light-years (914.7 parsecs) from the Solar System. First announced in 2010 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 1.7592% across the stellar disk), this world has a measured radius of 12.442 Earth radii (1.11 R♃), though radial-velocity mass constraints remain unmeasured in the current composite catalogue.

In its orbital architecture around KOI-217, KOI-217 b completes one full revolution every 3.905 Earth days at a semi-major axis of 0.0477 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 132.9 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 1046 K (+773°C / +1423°F) and receiving 272.03 S⊕ (~370,237 W/m²), KOI-217 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star KOI-217 is classified as a stellar host with an effective photospheric temperature of 5,545 K, a radius of 0.86 R☉, a mass of 0.95 M☉, an estimated bolometric luminosity of 0.627 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.7 Gyr and a metallicity of [Fe/H] = 0.12 dex (metal-rich relative to the Sun). From Earth, KOI-217 shines at apparent V-band magnitude 15.257 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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