HD 32518 b
Astrophysical Synthesis & Habitability Characterization
HD 32518 b is a confirmed gas giant exoplanet orbiting the star HD 32518, located approximately 398.3 light-years (122.12 parsecs) from the Solar System. First announced in 2009 by Thueringer Landessternwarte Tautenburg using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13.2 Earth radii (1.18 Jupiter radii) and has a measured mass of 905.493 Earth masses (2.85 Jupiter masses). Combining its mass and radius yields a mean bulk density of 2.17 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 5.2 g⊕ (50.99 m/s²), and an escape velocity of 92.6 km/s.
In its orbital architecture around HD 32518, HD 32518 b completes one full revolution every 157.35 Earth days at a semi-major axis of 0.594 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 41.1 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.028 (ranging from 0.5774 AU at periapsis to 0.6106 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 916 K (+643°C / +1189°F) and receiving 131.28 S⊕ (~178,671 W/m²), HD 32518 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 32518 is classified as an orange K-type star of spectral type K1 III with an effective photospheric temperature of 4,580 K, a radius of 10.22 R☉, a mass of 1.13 M☉, an estimated bolometric luminosity of 41.234 L☉. Stellar evolution modeling indicates an estimated stellar age of 5.83 Gyr and a metallicity of [Fe/H] = -0.15 dex (metal-poor relative to the Sun). From Earth, HD 32518 shines at apparent V-band magnitude 6.43 (accessible to binoculars and small amateur telescopes) 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: Thueringer Landessternwarte Tautenburg · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 32518 |
| Spectral Type | K1 III |
| Effective Temp (Teff) | 4,580 K |
| Stellar Radius | 10.2200 R☉ |
| Stellar Mass | 1.1300 M☉ |
| Bolometric Luminosity | 41.234 L☉ |
| Metallicity [Fe/H] | -0.150 dex |
| Stellar Age | 5.830 Gyr |
| Apparent Magnitude | V: 6.430 · G: 6.119 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.594000 AU |
| Orbital Period | 157.35 days |
| Mean Orbital Velocity | 41.1 km/s |
| Orbital Eccentricity (e) | 0.02800 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 2.17 g/cm³ (92.6 km/s vesc) |
| Insolation Flux | 131.2791 S⊕ (~178,671 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 398.300 LY (122.115 pc) |