HAT-P-25 b
Astrophysical Synthesis & Habitability Characterization
HAT-P-25 b is a confirmed gas giant exoplanet orbiting the star HAT-P-25, located approximately 979.7 light-years (300.38 parsecs) from the Solar System. First announced in 2012 by HATNet using the Transit detection technique (producing an estimated primary transit depth of 1.6107% across the stellar disk), this world measures 12.722 Earth radii (1.13 Jupiter radii) and has a measured mass of 180.845 Earth masses (0.57 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.48 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.12 g⊕ (10.98 m/s²), and an escape velocity of 42.2 km/s.
In its orbital architecture around HAT-P-25, HAT-P-25 b completes one full revolution every 3.653 Earth days at a semi-major axis of 0.0466 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 138.8 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.023 (ranging from 0.0455 AU at periapsis to 0.0477 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1182 K (+909°C / +1668°F) and receiving 325.00 S⊕ (~442,325 W/m²), HAT-P-25 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HAT-P-25 is classified as a solar-type yellow star of spectral type G5 with an effective photospheric temperature of 5,519 K, a radius of 0.919 R☉, a mass of 1.012 M☉, an estimated bolometric luminosity of 0.703 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.2 Gyr and a metallicity of [Fe/H] = 0.294 dex (metal-rich relative to the Sun). From Earth, HAT-P-25 shines at apparent V-band magnitude 13.146 (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-25 |
| Spectral Type | G5 |
| Effective Temp (Teff) | 5,519 K |
| Stellar Radius | 0.9190 R☉ |
| Stellar Mass | 1.0120 M☉ |
| Bolometric Luminosity | 0.703 L☉ |
| Metallicity [Fe/H] | 0.294 dex |
| Stellar Age | 3.200 Gyr |
| Apparent Magnitude | V: 13.146 · G: 12.842 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.046600 AU |
| Orbital Period | 3.653 days |
| Mean Orbital Velocity | 138.8 km/s |
| Orbital Eccentricity (e) | 0.02300 |
| Orbital Inclination (i) | 88.2200° |
| Mean Bulk Density | 0.48 g/cm³ (42.2 km/s vesc) |
| Insolation Flux | 325.0000 S⊕ (~442,325 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 979.700 LY (300.384 pc) |