HD 9446 b
Astrophysical Synthesis & Habitability Characterization
HD 9446 b is a confirmed gas giant exoplanet orbiting the star HD 9446, located approximately 164.2 light-years (50.35 parsecs) from the Solar System. First announced in 2009 by Haute-Provence Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 14 Earth radii (1.25 Jupiter radii) and has a measured mass of 222.472 Earth masses (0.7 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.45 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.14 g⊕ (11.18 m/s²), and an escape velocity of 44.6 km/s.
In its orbital architecture around HD 9446, HD 9446 b completes one full revolution every 30.052 Earth days at a semi-major axis of 0.189 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 68.4 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.2 carries the world between 0.1512 AU at periapsis and 0.2268 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 643 K (+370°C / +698°F) and receiving 30.79 S⊕ (~41,911 W/m²), HD 9446 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 9446 is classified as a solar-type yellow star of spectral type G5 V with an effective photospheric temperature of 5,793 K, a radius of 1 R☉, a mass of 1 M☉, an estimated bolometric luminosity of 1.01 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.09 dex (metal-rich relative to the Sun). From Earth, HD 9446 shines at apparent V-band magnitude 8.35 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere. The HD 9446 system is a multi-planet architecture hosting 2 confirmed worlds, with HD 9446 b sharing its stellar neighborhood alongside HD 9446 c.
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: Haute-Provence Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 9446 |
| Spectral Type | G5 V |
| Effective Temp (Teff) | 5,793 K |
| Stellar Radius | 1.0000 R☉ |
| Stellar Mass | 1.0000 M☉ |
| Bolometric Luminosity | 1.01 L☉ |
| Metallicity [Fe/H] | 0.090 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 8.350 · G: 8.210 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.189000 AU |
| Orbital Period | 30.052 days |
| Mean Orbital Velocity | 68.4 km/s |
| Orbital Eccentricity (e) | 0.20000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.45 g/cm³ (44.6 km/s vesc) |
| Insolation Flux | 30.7942 S⊕ (~41,911 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 164.200 LY (50.350 pc) |