HAT-P-13 b
Astrophysical Synthesis & Habitability Characterization
HAT-P-13 b is a confirmed gas giant exoplanet orbiting the star HAT-P-13, located approximately 805 light-years (246.81 parsecs) from the Solar System. First announced in 2009 by HATNet using the Transit detection technique (producing an estimated primary transit depth of 0.5541% across the stellar disk), this world measures 14.258 Earth radii (1.27 Jupiter radii) and has a measured mass of 270.462 Earth masses (0.85 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.51 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 48.7 km/s.
In its orbital architecture around HAT-P-13, HAT-P-13 b completes one full revolution every 2.916 Earth days at a semi-major axis of 0.04383 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 163.5 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.0133 (ranging from 0.0432 AU at periapsis to 0.0444 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1740 K (+1467°C / +2673°F) and receiving 1,978.52 S⊕ (~2,692,772 W/m²), HAT-P-13 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HAT-P-13 is classified as a solar-type yellow star of spectral type G4 with an effective photospheric temperature of 5,653 K, a radius of 1.756 R☉, a mass of 1.32 M☉, an estimated bolometric luminosity of 2.825 L☉. Stellar evolution modeling indicates an estimated stellar age of 5 Gyr and a metallicity of [Fe/H] = 0.46 dex (metal-rich relative to the Sun). From Earth, HAT-P-13 shines at apparent V-band magnitude 10.421 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The HAT-P-13 system is a multi-planet architecture hosting 2 confirmed worlds, with HAT-P-13 b sharing its stellar neighborhood alongside HAT-P-13 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-13 |
| Spectral Type | G4 |
| Effective Temp (Teff) | 5,653 K |
| Stellar Radius | 1.7560 R☉ |
| Stellar Mass | 1.3200 M☉ |
| Bolometric Luminosity | 2.825 L☉ |
| Metallicity [Fe/H] | 0.460 dex |
| Stellar Age | 5.000 Gyr |
| Apparent Magnitude | V: 10.421 · G: 10.417 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.043830 AU |
| Orbital Period | 2.916 days |
| Mean Orbital Velocity | 163.5 km/s |
| Orbital Eccentricity (e) | 0.01330 |
| Orbital Inclination (i) | 83.4000° |
| Mean Bulk Density | 0.51 g/cm³ (48.7 km/s vesc) |
| Insolation Flux | 1978.5245 S⊕ (~2,692,772 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 805.000 LY (246.810 pc) |