HAT-P-5 b
Astrophysical Synthesis & Habitability Characterization
HAT-P-5 b is a confirmed gas giant exoplanet orbiting the star HAT-P-5, located approximately 989.3 light-years (303.34 parsecs) from the Solar System. First announced in 2007 by HATNet using the Transit detection technique (producing an estimated primary transit depth of 1.2326% across the stellar disk), this world measures 13.563 Earth radii (1.21 Jupiter radii) and has a measured mass of 311.473 Earth masses (0.98 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.69 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.69 g⊕ (16.57 m/s²), and an escape velocity of 53.6 km/s.
In its orbital architecture around HAT-P-5, HAT-P-5 b completes one full revolution every 2.788 Earth days at a semi-major axis of 0.04073 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 158.9 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 1517 K (+1244°C / +2271°F) and receiving 850.68 S⊕ (~1,157,769 W/m²), HAT-P-5 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HAT-P-5 is classified as a solar-type yellow star of spectral type G with an effective photospheric temperature of 5,960 K, a radius of 1.12 R☉, a mass of 1.04 M☉, an estimated bolometric luminosity of 1.42 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.6 Gyr and a metallicity of [Fe/H] = 0.24 dex (metal-rich relative to the Sun). From Earth, HAT-P-5 shines at apparent V-band magnitude 11.954 (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-5 |
| Spectral Type | G |
| Effective Temp (Teff) | 5,960 K |
| Stellar Radius | 1.1200 R☉ |
| Stellar Mass | 1.0400 M☉ |
| Bolometric Luminosity | 1.42 L☉ |
| Metallicity [Fe/H] | 0.240 dex |
| Stellar Age | 2.600 Gyr |
| Apparent Magnitude | V: 11.954 · G: 11.822 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.040730 AU |
| Orbital Period | 2.788 days |
| Mean Orbital Velocity | 158.9 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 86.7500° |
| Mean Bulk Density | 0.69 g/cm³ (53.6 km/s vesc) |
| Insolation Flux | 850.6754 S⊕ (~1,157,769 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 989.300 LY (303.336 pc) |