HAT-P-59 b
Astrophysical Synthesis & Habitability Characterization
HAT-P-59 b is a confirmed gas giant exoplanet orbiting the star HAT-P-59, located approximately 865.8 light-years (265.47 parsecs) from the Solar System. First announced in 2021 by HATNet using the Transit detection technique (producing an estimated primary transit depth of 1.0931% across the stellar disk), this world measures 12.588 Earth radii (1.12 Jupiter radii) and has a measured mass of 489.456 Earth masses (1.54 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.35 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 3.09 g⊕ (30.3 m/s²), and an escape velocity of 69.8 km/s.
In its orbital architecture around HAT-P-59, HAT-P-59 b completes one full revolution every 4.142 Earth days at a semi-major axis of 0.05064 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 133 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.03 (ranging from 0.0491 AU at periapsis to 0.0522 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1278 K (+1005°C / +1841°F) and receiving 441.40 S⊕ (~600,745 W/m²), HAT-P-59 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HAT-P-59 is classified as a stellar host with an effective photospheric temperature of 5,678 K, a radius of 1.1038 R☉, a mass of 1.008 M☉, an estimated bolometric luminosity of 1.136 L☉. Stellar evolution modeling indicates an estimated stellar age of 7.3 Gyr and a metallicity of [Fe/H] = 0.217 dex (metal-rich relative to the Sun). From Earth, HAT-P-59 shines at apparent V-band magnitude 11.64 (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-59 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,678 K |
| Stellar Radius | 1.1038 R☉ |
| Stellar Mass | 1.0080 M☉ |
| Bolometric Luminosity | 1.136 L☉ |
| Metallicity [Fe/H] | 0.217 dex |
| Stellar Age | 7.300 Gyr |
| Apparent Magnitude | V: 11.640 · G: 11.679 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.050640 AU |
| Orbital Period | 4.142 days |
| Mean Orbital Velocity | 133 km/s |
| Orbital Eccentricity (e) | 0.03000 |
| Orbital Inclination (i) | 85.1800° |
| Mean Bulk Density | 1.35 g/cm³ (69.8 km/s vesc) |
| Insolation Flux | 441.4000 S⊕ (~600,745 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 865.800 LY (265.471 pc) |