HAT-P-1 b

Astrophysical Synthesis & Habitability Characterization

HAT-P-1 b is a confirmed gas giant exoplanet orbiting the star HAT-P-1, located approximately 518.5 light-years (158.98 parsecs) from the Solar System. First announced in 2006 by HATNet using the Transit detection technique (producing an estimated primary transit depth of 1.3331% across the stellar disk), this world measures 14.785 Earth radii (1.32 Jupiter radii) and has a measured mass of 166.861 Earth masses (0.53 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.28 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.76 g⊕ (7.45 m/s²), and an escape velocity of 37.6 km/s.

In its orbital architecture around HAT-P-1, HAT-P-1 b completes one full revolution every 4.465 Earth days at a semi-major axis of 0.05561 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 135.5 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 1322 K (+1049°C / +1920°F) and receiving 259.69 S⊕ (~353,434 W/m²), HAT-P-1 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star HAT-P-1 is classified as a solar-type yellow star of spectral type G0 V with an effective photospheric temperature of 5,980 K, a radius of 1.174 R☉, a mass of 1.151 M☉, an estimated bolometric luminosity of 1.581 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.6 Gyr and a metallicity of [Fe/H] = 0.13 dex (metal-rich relative to the Sun). From Earth, HAT-P-1 shines at apparent V-band magnitude 9.827 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere.

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