HAT-P-15 b
Astrophysical Synthesis & Habitability Characterization
HAT-P-15 b is a confirmed gas giant exoplanet orbiting the star HAT-P-15, located approximately 627.9 light-years (192.52 parsecs) from the Solar System. First announced in 2010 by HATNet using the Transit detection technique (producing an estimated primary transit depth of 1.0365% across the stellar disk), this world measures 11.882 Earth radii (1.06 Jupiter radii) and has a measured mass of 616.59 Earth masses (1.94 Jupiter masses). Combining its mass and radius yields a mean bulk density of 2.03 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 4.37 g⊕ (42.86 m/s²), and an escape velocity of 80.6 km/s.
In its orbital architecture around HAT-P-15, HAT-P-15 b completes one full revolution every 10.864 Earth days at a semi-major axis of 0.0965 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 96.6 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.19 carries the world between 0.0782 AU at periapsis and 0.1148 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 904 K (+631°C / +1168°F) and receiving 79.76 S⊕ (~108,550 W/m²), HAT-P-15 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HAT-P-15 is classified as a solar-type yellow star of spectral type G5 with an effective photospheric temperature of 5,568 K, a radius of 1.07 R☉, a mass of 1 M☉, an estimated bolometric luminosity of 0.987 L☉. Stellar evolution modeling indicates an estimated stellar age of 6.8 Gyr and a metallicity of [Fe/H] = 0.22 dex (metal-rich relative to the Sun). From Earth, HAT-P-15 shines at apparent V-band magnitude 12.41 (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-15 |
| Spectral Type | G5 |
| Effective Temp (Teff) | 5,568 K |
| Stellar Radius | 1.0700 R☉ |
| Stellar Mass | 1.0000 M☉ |
| Bolometric Luminosity | 0.987 L☉ |
| Metallicity [Fe/H] | 0.220 dex |
| Stellar Age | 6.800 Gyr |
| Apparent Magnitude | V: 12.410 · G: 11.723 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.096500 AU |
| Orbital Period | 10.864 days |
| Mean Orbital Velocity | 96.6 km/s |
| Orbital Eccentricity (e) | 0.19000 |
| Orbital Inclination (i) | 89.1000° |
| Mean Bulk Density | 2.03 g/cm³ (80.6 km/s vesc) |
| Insolation Flux | 79.7578 S⊕ (~108,550 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 627.900 LY (192.516 pc) |