HD 164922 b
Astrophysical Synthesis & Habitability Characterization
HD 164922 b is a confirmed gas giant exoplanet orbiting the star HD 164922, located approximately 71.8 light-years (22 parsecs) from the Solar System. First announced in 2005 by W. M. Keck Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13.3 Earth radii (1.19 Jupiter radii) and has a measured mass of 116 Earth masses (0.36 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.27 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.66 g⊕ (6.47 m/s²), and an escape velocity of 33 km/s.
In its orbital architecture around HD 164922, HD 164922 b completes one full revolution every 1207 Earth days (3.3Julian years) at a semi-major axis of 2.16 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 19.5 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.08 carries the world between 1.9872 AU at periapsis and 2.3328 AU at apoapsis, driving measurable seasonal insolation cycles.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 159 K (-114°C / -173°F) and an incident flux of 0.16 S⊕ (~215 W/m²), surface water and volatile species on HD 164922 b would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star HD 164922 is classified as a solar-type yellow star of spectral type G9 V with an effective photospheric temperature of 5,390 K, a radius of 0.946 R☉, a mass of 0.926 M☉, an estimated bolometric luminosity of 0.678 L☉. Stellar evolution modeling indicates an estimated stellar age of 9.58 Gyr and a metallicity of [Fe/H] = 0.18 dex (metal-rich relative to the Sun). From Earth, HD 164922 shines at apparent V-band magnitude 7.012 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere. The HD 164922 system is a multi-planet architecture hosting 4 confirmed worlds, with HD 164922 b sharing its stellar neighborhood alongside HD 164922 d, HD 164922 e, HD 164922 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: W. M. Keck Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 164922 |
| Spectral Type | G9 V |
| Effective Temp (Teff) | 5,390 K |
| Stellar Radius | 0.9460 R☉ |
| Stellar Mass | 0.9260 M☉ |
| Bolometric Luminosity | 0.678 L☉ |
| Metallicity [Fe/H] | 0.180 dex |
| Stellar Age | 9.580 Gyr |
| Apparent Magnitude | V: 7.012 · G: 6.786 |
| System Architecture | 1 Star, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 2.160000 AU |
| Orbital Period | 1207 days |
| Mean Orbital Velocity | 19.5 km/s |
| Orbital Eccentricity (e) | 0.08000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.27 g/cm³ (33 km/s vesc) |
| Insolation Flux | 0.1578 S⊕ (~215 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 71.800 LY (22.002 pc) |