HD 8673 b
Astrophysical Synthesis & Habitability Characterization
HD 8673 b is a confirmed gas giant exoplanet orbiting the star HD 8673, located approximately 123.5 light-years (37.86 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 12.3 Earth radii (1.1 Jupiter radii) and has a measured mass of 4210.591 Earth masses (13.25 Jupiter masses). Combining its mass and radius yields a mean bulk density of 12.48 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 27.83 g⊕ (272.92 m/s²), and an escape velocity of 207 km/s.
In its orbital architecture around HD 8673, HD 8673 b completes one full revolution every 1644.691 Earth days (4.5Julian years) at a semi-major axis of 2.97 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 19.6 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.73, swinging from 0.8019 AU at periapsis out to 5.1381 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 12.300 R⊕, HD 8673 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 8673 is classified as a warm F-type star of spectral type F5 with an effective photospheric temperature of 6,389 K, a radius of 1.5023 R☉, a mass of 1.28 M☉, an estimated bolometric luminosity of 3.374 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.147 dex (metal-rich relative to the Sun). From Earth, HD 8673 shines at apparent V-band magnitude 6.331 (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 8673 |
| Spectral Type | F5 |
| Effective Temp (Teff) | 6,389 K |
| Stellar Radius | 1.5023 R☉ |
| Stellar Mass | 1.2800 M☉ |
| Bolometric Luminosity | 3.374 L☉ |
| Metallicity [Fe/H] | 0.147 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 6.331 · G: 6.224 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 2.970000 AU |
| Orbital Period | 1644.691 days |
| Mean Orbital Velocity | 19.6 km/s |
| Orbital Eccentricity (e) | 0.73000 |
| Orbital Inclination (i) | 95.4500° |
| Mean Bulk Density | 12.48 g/cm³ (207 km/s vesc) |
| Insolation Flux | 0.3841 S⊕ (~523 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 123.500 LY (37.862 pc) |