HD 9446 c
Astrophysical Synthesis & Habitability Characterization
HD 9446 c 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 13.4 Earth radii (1.2 Jupiter radii) and has a measured mass of 578.426 Earth masses (1.82 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.33 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 3.22 g⊕ (31.58 m/s²), and an escape velocity of 73.5 km/s.
In its orbital architecture around HD 9446, HD 9446 c completes one full revolution every 192.9 Earth days at a semi-major axis of 0.654 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 36.9 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.06 carries the world between 0.6148 AU at periapsis and 0.6932 AU at apoapsis, driving measurable seasonal insolation cycles.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 13.400 R⊕, HD 9446 c 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 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 c sharing its stellar neighborhood alongside HD 9446 b.
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) | 0.654000 AU |
| Orbital Period | 192.9 days |
| Mean Orbital Velocity | 36.9 km/s |
| Orbital Eccentricity (e) | 0.06000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.33 g/cm³ (73.5 km/s vesc) |
| Insolation Flux | 2.5718 S⊕ (~3,500 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 164.200 LY (50.350 pc) |