KELT-17 b

Astrophysical Synthesis & Habitability Characterization

KELT-17 b is a confirmed gas giant exoplanet orbiting the star KELT-17, located approximately 738.7 light-years (226.5 parsecs) from the Solar System. First announced in 2016 by KELT using the Transit detection technique (producing an estimated primary transit depth of 0.9076% across the stellar disk), this world measures 17.094 Earth radii (1.53 Jupiter radii) and has a measured mass of 416.357 Earth masses (1.31 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.46 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.42 g⊕ (13.93 m/s²), and an escape velocity of 55.2 km/s.

In its orbital architecture around KELT-17, KELT-17 b completes one full revolution every 3.08 Earth days at a semi-major axis of 0.04881 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 172.4 km/s (compared to Earth's 29.8 km/s).

⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 2087 K (+1814°C / +3297°F) and receiving 3,331.87 S⊕ (~4,534,676 W/m²), KELT-17 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star KELT-17 is classified as a luminous A-type star of spectral type A with an effective photospheric temperature of 7,454 K, a radius of 1.645 R☉, a mass of 1.635 M☉, an estimated bolometric luminosity of 7.495 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.65 Gyr and a metallicity of [Fe/H] = -0.018 dex (near-solar heavy-element abundance). From Earth, KELT-17 shines at apparent V-band magnitude 9.234 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere.

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