HAT-P-22 b
Astrophysical Synthesis & Habitability Characterization
HAT-P-22 b is a confirmed gas giant exoplanet orbiting the star HAT-P-22, located approximately 266.7 light-years (81.77 parsecs) from the Solar System. First announced in 2010 by HATNet using the Transit detection technique (producing an estimated primary transit depth of 1.1334% across the stellar disk), this world measures 12.89 Earth radii (1.15 Jupiter radii) and has a measured mass of 785.04 Earth masses (2.47 Jupiter masses). Combining its mass and radius yields a mean bulk density of 2.02 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 4.72 g⊕ (46.29 m/s²), and an escape velocity of 87.3 km/s.
In its orbital architecture around HAT-P-22, HAT-P-22 b completes one full revolution every 3.212 Earth days at a semi-major axis of 0.0414 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 140.2 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.02 (ranging from 0.0406 AU at periapsis to 0.0422 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1463 K (+1190°C / +2174°F) and receiving 325.57 S⊕ (~443,099 W/m²), HAT-P-22 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HAT-P-22 is classified as a solar-type yellow star of spectral type G5 V with an effective photospheric temperature of 5,302 K, a radius of 1.11 R☉, a mass of 1.13 M☉, an estimated bolometric luminosity of 0.874 L☉. Stellar evolution modeling indicates an estimated stellar age of 12.4 Gyr and a metallicity of [Fe/H] = 0.24 dex (metal-rich relative to the Sun). From Earth, HAT-P-22 shines at apparent V-band magnitude 9.763 (accessible to binoculars and small amateur telescopes) 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-22 |
| Spectral Type | G5 V |
| Effective Temp (Teff) | 5,302 K |
| Stellar Radius | 1.1100 R☉ |
| Stellar Mass | 1.1300 M☉ |
| Bolometric Luminosity | 0.874 L☉ |
| Metallicity [Fe/H] | 0.240 dex |
| Stellar Age | 12.400 Gyr |
| Apparent Magnitude | V: 9.763 · G: 9.519 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.041400 AU |
| Orbital Period | 3.212 days |
| Mean Orbital Velocity | 140.2 km/s |
| Orbital Eccentricity (e) | 0.02000 |
| Orbital Inclination (i) | 86.9000° |
| Mean Bulk Density | 2.02 g/cm³ (87.3 km/s vesc) |
| Insolation Flux | 325.5690 S⊕ (~443,099 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 266.700 LY (81.765 pc) |