HAT-P-3 b
Astrophysical Synthesis & Habitability Characterization
HAT-P-3 b is a confirmed gas giant exoplanet orbiting the star HAT-P-3, located approximately 438.9 light-years (134.55 parsecs) from the Solar System. First announced in 2007 by HATNet using the Transit detection technique (producing an estimated primary transit depth of 1.2327% across the stellar disk), this world measures 10.536 Earth radii (0.94 Jupiter radii) and has a measured mass of 206.59 Earth masses (0.65 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.97 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.86 g⊕ (18.24 m/s²), and an escape velocity of 49.5 km/s.
In its orbital architecture around HAT-P-3, HAT-P-3 b completes one full revolution every 2.9 Earth days at a semi-major axis of 0.03866 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 145 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 1189 K (+916°C / +1681°F) and receiving 176.59 S⊕ (~240,335 W/m²), HAT-P-3 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HAT-P-3 is classified as an orange K-type star of spectral type K1 with an effective photospheric temperature of 5,185 K, a radius of 0.87 R☉, a mass of 1.06 M☉, an estimated bolometric luminosity of 0.491 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.6 Gyr and a metallicity of [Fe/H] = 0.27 dex (metal-rich relative to the Sun). From Earth, HAT-P-3 shines at apparent V-band magnitude 11.856 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.
Methodology: Computed using the Schulze-Makuch et al. (2011) weighted metric comparing physical interior (radius, estimated density) and surface thermal regime (escape velocity, equilibrium temperature).
Discovery Facility: HATNet · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HAT-P-3 |
| Spectral Type | K1 |
| Effective Temp (Teff) | 5,185 K |
| Stellar Radius | 0.8700 R☉ |
| Stellar Mass | 1.0600 M☉ |
| Bolometric Luminosity | 0.491 L☉ |
| Metallicity [Fe/H] | 0.270 dex |
| Stellar Age | 1.600 Gyr |
| Apparent Magnitude | V: 11.856 · G: 11.280 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.038660 AU |
| Orbital Period | 2.9 days |
| Mean Orbital Velocity | 145 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 87.2400° |
| Mean Bulk Density | 0.97 g/cm³ (49.5 km/s vesc) |
| Insolation Flux | 176.5870 S⊕ (~240,335 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 438.900 LY (134.554 pc) |