HD 224538 b
Astrophysical Synthesis & Habitability Characterization
HD 224538 b is a confirmed gas giant exoplanet orbiting the star HD 224538, located approximately 257.9 light-years (79.06 parsecs) from the Solar System. First announced in 2016 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 12.7 Earth radii (1.13 Jupiter radii) and has a measured mass of 2075.737 Earth masses (6.53 Jupiter masses). Combining its mass and radius yields a mean bulk density of 5.59 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 12.87 g⊕ (126.21 m/s²), and an escape velocity of 143 km/s.
In its orbital architecture around HD 224538, HD 224538 b completes one full revolution every 1202.052 Earth days (3.29Julian years) at a semi-major axis of 2.375 AU (corresponding to the middle-system regime between Mars at 1.52 AU and Jupiter at 5.20 AU). Its mean orbital velocity is approximately 21.5 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.476, swinging from 1.2445 AU at periapsis out to 3.5055 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 12.700 R⊕, HD 224538 b 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 HD 224538 is classified as a warm F-type star of spectral type F8/G0 IV/V with an effective photospheric temperature of 6,097 K, a radius of 1.54 R☉, a mass of 1.23 M☉, an estimated bolometric luminosity of 2.94 L☉. Stellar evolution modeling indicates an estimated stellar age of 2 Gyr and a metallicity of [Fe/H] = 0.27 dex (metal-rich relative to the Sun). From Earth, HD 224538 shines at apparent V-band magnitude 8.06 (accessible to binoculars and small amateur telescopes) in the Southern 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: Multiple Observatories · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 224538 |
| Spectral Type | F8/G0 IV/V |
| Effective Temp (Teff) | 6,097 K |
| Stellar Radius | 1.5400 R☉ |
| Stellar Mass | 1.2300 M☉ |
| Bolometric Luminosity | 2.94 L☉ |
| Metallicity [Fe/H] | 0.270 dex |
| Stellar Age | 2.000 Gyr |
| Apparent Magnitude | V: 8.060 · G: 7.922 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 2.375000 AU |
| Orbital Period | 1202.052 days |
| Mean Orbital Velocity | 21.5 km/s |
| Orbital Eccentricity (e) | 0.47600 |
| Orbital Inclination (i) | 91.1250° |
| Mean Bulk Density | 5.59 g/cm³ (143 km/s vesc) |
| Insolation Flux | 0.5230 S⊕ (~712 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 257.900 LY (79.061 pc) |