HAT-P-56 b
Astrophysical Synthesis & Habitability Characterization
HAT-P-56 b is a confirmed gas giant exoplanet orbiting the star HAT-P-56, located approximately 1045.8 light-years (320.64 parsecs) from the Solar System. First announced in 2015 by HATNet using the Transit detection technique (producing an estimated primary transit depth of 1.1143% across the stellar disk), this world measures 16.926 Earth radii (1.51 Jupiter radii) and has a measured mass of 734.187 Earth masses (2.31 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.83 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 2.56 g⊕ (25.11 m/s²), and an escape velocity of 73.7 km/s.
In its orbital architecture around HAT-P-56, HAT-P-56 b completes one full revolution every 2.791 Earth days at a semi-major axis of 0.0423 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 164.9 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.29, swinging from 0.03 AU at periapsis out to 0.0546 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1840 K (+1567°C / +2853°F) and receiving 3,515.00 S⊕ (~4,783,915 W/m²), HAT-P-56 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HAT-P-56 is classified as a warm F-type star of spectral type F8 with an effective photospheric temperature of 6,566 K, a radius of 1.47 R☉, a mass of 1.42 M☉, an estimated bolometric luminosity of 3.604 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.01 Gyr and a metallicity of [Fe/H] = 0 dex (near-solar heavy-element abundance). From Earth, HAT-P-56 shines at apparent V-band magnitude 10.92 (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-56 |
| Spectral Type | F8 |
| Effective Temp (Teff) | 6,566 K |
| Stellar Radius | 1.4700 R☉ |
| Stellar Mass | 1.4200 M☉ |
| Bolometric Luminosity | 3.604 L☉ |
| Metallicity [Fe/H] | 0.000 dex |
| Stellar Age | 2.010 Gyr |
| Apparent Magnitude | V: 10.920 · G: 10.825 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.042300 AU |
| Orbital Period | 2.791 days |
| Mean Orbital Velocity | 164.9 km/s |
| Orbital Eccentricity (e) | 0.29000 |
| Orbital Inclination (i) | 82.1300° |
| Mean Bulk Density | 0.83 g/cm³ (73.7 km/s vesc) |
| Insolation Flux | 3515.0000 S⊕ (~4,783,915 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1045.800 LY (320.639 pc) |