HAT-P-40 b

Astrophysical Synthesis & Habitability Characterization

HAT-P-40 b is a confirmed gas giant exoplanet orbiting the star HAT-P-40, located approximately 1514.9 light-years (464.47 parsecs) from the Solar System. First announced in 2012 by HATNet using the Transit detection technique (producing an estimated primary transit depth of 0.6483% across the stellar disk), this world measures 17.038 Earth radii (1.52 Jupiter radii) and has a measured mass of 152.558 Earth masses (0.48 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.17 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.53 g⊕ (5.2 m/s²), and an escape velocity of 33.5 km/s.

In its orbital architecture around HAT-P-40, HAT-P-40 b completes one full revolution every 4.457 Earth days at a semi-major axis of 0.0608 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 148.4 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 1770 K (+1497°C / +2727°F) and receiving 1,747.42 S⊕ (~2,378,232 W/m²), HAT-P-40 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star HAT-P-40 is classified as a stellar host with an effective photospheric temperature of 6,080 K, a radius of 1.94 R☉, a mass of 1.03 M☉, an estimated bolometric luminosity of 4.614 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.7 Gyr and a metallicity of [Fe/H] = 0.22 dex (metal-rich relative to the Sun). From Earth, HAT-P-40 shines at apparent V-band magnitude 11.34 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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