HAT-P-13 c
Astrophysical Synthesis & Habitability Characterization
HAT-P-13 c 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 W. M. Keck Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 12.3 Earth radii (1.1 Jupiter radii) and has a measured mass of 4538.421 Earth masses (14.28 Jupiter masses). Combining its mass and radius yields a mean bulk density of 13.45 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 30 g⊕ (294.2 m/s²), and an escape velocity of 214.9 km/s.
In its orbital architecture around HAT-P-13, HAT-P-13 c completes one full revolution every 446.27 Earth days (1.22Julian years) at a semi-major axis of 1.258 AU (comparable to the inner terrestrial zone between Venus, Earth at 1.00 AU, and Mars at 1.52 AU). Its mean orbital velocity is approximately 30.7 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.6616, swinging from 0.4257 AU at periapsis out to 2.0903 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 12.300 R⊕, HAT-P-13 c exceeds the empirical ~1.8–2.2 R⊕ Fulton radius valley threshold, indicating a substantial hydrogen-helium or supercritical volatile envelope without a conventional solid terrestrial surface.
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 c sharing its stellar neighborhood alongside HAT-P-13 b.
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: W. M. Keck Observatory · 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) | 1.258000 AU |
| Orbital Period | 446.27 days |
| Mean Orbital Velocity | 30.7 km/s |
| Orbital Eccentricity (e) | 0.66160 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 13.45 g/cm³ (214.9 km/s vesc) |
| Insolation Flux | 1.4016 S⊕ (~1,908 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 805.000 LY (246.810 pc) |