HAT-P-57 b
Astrophysical Synthesis & Habitability Characterization
HAT-P-57 b is a confirmed gas giant exoplanet orbiting the star HAT-P-57, located approximately 912.8 light-years (279.86 parsecs) from the Solar System. First announced in 2015 by HATNet using the Transit detection technique (producing an estimated primary transit depth of 0.9342% across the stellar disk), this world measures 19.504 Earth radii (1.74 Jupiter radii) and has a measured mass of 448.14 Earth masses (1.41 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.33 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.18 g⊕ (11.57 m/s²), and an escape velocity of 53.6 km/s.
In its orbital architecture around HAT-P-57, HAT-P-57 b completes one full revolution every 2.465 Earth days at a semi-major axis of 0.0406 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 179.2 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 2200 K (+1927°C / +3501°F) and receiving 2,726.63 S⊕ (~3,710,947 W/m²), HAT-P-57 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HAT-P-57 is classified as a luminous A-type star of spectral type A8 V with an effective photospheric temperature of 6,330 K, a radius of 1.85 R☉, a mass of 2.77 M☉, an estimated bolometric luminosity of 4.93 L☉. Stellar evolution modeling indicates an estimated stellar age of 1 Gyr and a metallicity of [Fe/H] = -0.25 dex (metal-poor relative to the Sun). From Earth, HAT-P-57 shines at apparent V-band magnitude 10.639 (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-57 |
| Spectral Type | A8 V |
| Effective Temp (Teff) | 6,330 K |
| Stellar Radius | 1.8500 R☉ |
| Stellar Mass | 2.7700 M☉ |
| Bolometric Luminosity | 4.93 L☉ |
| Metallicity [Fe/H] | -0.250 dex |
| Stellar Age | 1.000 Gyr |
| Apparent Magnitude | V: 10.639 · G: 10.425 |
| System Architecture | 3 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.040600 AU |
| Orbital Period | 2.465 days |
| Mean Orbital Velocity | 179.2 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 88.2600° |
| Mean Bulk Density | 0.33 g/cm³ (53.6 km/s vesc) |
| Insolation Flux | 2726.6328 S⊕ (~3,710,947 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 912.800 LY (279.860 pc) |