HD 164922 d
Astrophysical Synthesis & Habitability Characterization
HD 164922 d is a confirmed super-earth exoplanet orbiting the star HD 164922, located approximately 71.8 light-years (22 parsecs) from the Solar System. First announced in 2020 by Roque de los Muchachos Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 1.83 Earth radii and has a measured mass of 4 Earth masses. Combining its mass and radius yields a mean bulk density of 3.6 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.19 g⊕ (11.67 m/s²), and an escape velocity of 16.5 km/s.
In its orbital architecture around HD 164922, HD 164922 d completes one full revolution every 12.458 Earth days at a semi-major axis of 0.103 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 89.9 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.12 carries the world between 0.0906 AU at periapsis and 0.1154 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 788 K (+515°C / +959°F) and receiving 66.92 S⊕ (~91,084 W/m²), HD 164922 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
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 d sharing its stellar neighborhood alongside HD 164922 e, HD 164922 c, HD 164922 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: Roque de los Muchachos 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) | 0.103000 AU |
| Orbital Period | 12.458 days |
| Mean Orbital Velocity | 89.9 km/s |
| Orbital Eccentricity (e) | 0.12000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 3.6 g/cm³ (16.5 km/s vesc) |
| Insolation Flux | 66.9243 S⊕ (~91,084 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 71.800 LY (22.002 pc) |