HD 9174 b
Astrophysical Synthesis & Habitability Characterization
HD 9174 b is a confirmed gas giant exoplanet orbiting the star HD 9174, located approximately 265.8 light-years (81.49 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 13.7 Earth radii (1.22 Jupiter radii) and has a measured mass of 352.791 Earth masses (1.11 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.76 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.88 g⊕ (18.44 m/s²), and an escape velocity of 56.8 km/s.
In its orbital architecture around HD 9174, HD 9174 b completes one full revolution every 1179 Earth days (3.23Julian years) at a semi-major axis of 2.2 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 20.3 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.12 carries the world between 1.936 AU at periapsis and 2.464 AU at apoapsis, driving measurable seasonal insolation cycles.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 13.700 R⊕, HD 9174 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 9174 is classified as a solar-type yellow star of spectral type G8 IV with an effective photospheric temperature of 5,577 K, a radius of 1.67 R☉, a mass of 1.03 M☉, an estimated bolometric luminosity of 2.421 L☉. Stellar evolution modeling indicates an estimated stellar age of 9 Gyr and a metallicity of [Fe/H] = 0.39 dex (metal-rich relative to the Sun). From Earth, HD 9174 shines at apparent V-band magnitude 8.4 (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 9174 |
| Spectral Type | G8 IV |
| Effective Temp (Teff) | 5,577 K |
| Stellar Radius | 1.6700 R☉ |
| Stellar Mass | 1.0300 M☉ |
| Bolometric Luminosity | 2.421 L☉ |
| Metallicity [Fe/H] | 0.390 dex |
| Stellar Age | 9.000 Gyr |
| Apparent Magnitude | V: 8.400 · G: 8.229 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 2.200000 AU |
| Orbital Period | 1179 days |
| Mean Orbital Velocity | 20.3 km/s |
| Orbital Eccentricity (e) | 0.12000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.76 g/cm³ (56.8 km/s vesc) |
| Insolation Flux | 0.4979 S⊕ (~678 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 265.800 LY (81.489 pc) |