HAT-P-17 b
Astrophysical Synthesis & Habitability Characterization
HAT-P-17 b is a confirmed gas giant exoplanet orbiting the star HAT-P-17, located approximately 301.3 light-years (92.38 parsecs) from the Solar System. First announced in 2012 by HATNet using the Transit detection technique (producing an estimated primary transit depth of 1.5381% across the stellar disk), this world measures 11.769 Earth radii (1.05 Jupiter radii) and has a measured mass of 184.341 Earth masses (0.58 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.62 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.33 g⊕ (13.04 m/s²), and an escape velocity of 44.3 km/s.
In its orbital architecture around HAT-P-17, HAT-P-17 b completes one full revolution every 10.339 Earth days at a semi-major axis of 0.0892 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 93.9 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.35, swinging from 0.058 AU at periapsis out to 0.1204 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 800 K (+527°C / +981°F) and receiving 110.51 S⊕ (~150,407 W/m²), HAT-P-17 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HAT-P-17 is classified as an orange K-type star of spectral type K with an effective photospheric temperature of 5,246 K, a radius of 0.87 R☉, a mass of 0.99 M☉, an estimated bolometric luminosity of 0.514 L☉. Stellar evolution modeling indicates an estimated stellar age of 7 Gyr and a metallicity of [Fe/H] = 0 dex (near-solar heavy-element abundance). From Earth, HAT-P-17 shines at apparent V-band magnitude 10.375 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The HAT-P-17 system is a multi-planet architecture hosting 2 confirmed worlds, with HAT-P-17 b sharing its stellar neighborhood alongside HAT-P-17 c.
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-17 |
| Spectral Type | K |
| Effective Temp (Teff) | 5,246 K |
| Stellar Radius | 0.8700 R☉ |
| Stellar Mass | 0.9900 M☉ |
| Bolometric Luminosity | 0.514 L☉ |
| Metallicity [Fe/H] | 0.000 dex |
| Stellar Age | 7.000 Gyr |
| Apparent Magnitude | V: 10.375 · G: 10.274 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.089200 AU |
| Orbital Period | 10.339 days |
| Mean Orbital Velocity | 93.9 km/s |
| Orbital Eccentricity (e) | 0.35000 |
| Orbital Inclination (i) | 89.2000° |
| Mean Bulk Density | 0.62 g/cm³ (44.3 km/s vesc) |
| Insolation Flux | 110.5120 S⊕ (~150,407 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 301.300 LY (92.383 pc) |