HD 219134 g
Astrophysical Synthesis & Habitability Characterization
HD 219134 g is a confirmed sub-neptune exoplanet orbiting the star HD 219134, located approximately 21.3 light-years (6.53 parsecs) from the Solar System. First announced in 2015 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 3.28 Earth radii (0.29 Jupiter radii) and has a measured mass of 10.806 Earth masses. Combining its mass and radius yields a mean bulk density of 1.69 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1 g⊕ (9.81 m/s²), and an escape velocity of 20.3 km/s.
In its orbital architecture around HD 219134, HD 219134 g completes one full revolution every 94.2 Earth days at a semi-major axis of 0.3753 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 43.3 km/s (compared to Earth's 29.8 km/s). The orbit is modeled as circular (e = 0.00), maintaining a constant stellar distance throughout its year.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 3.280 R⊕, HD 219134 g 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 219134 is classified as an orange K-type star of spectral type K3 V with an effective photospheric temperature of 4,913 K, a radius of 0.77 R☉, a mass of 0.794 M☉, an estimated bolometric luminosity of 0.31 L☉. Stellar evolution modeling indicates an estimated stellar age of 12.46 Gyr and a metallicity of [Fe/H] = 0.08 dex (metal-rich relative to the Sun). From Earth, HD 219134 shines at apparent V-band magnitude 5.569 (visible to the unaided human eye under dark skies) in the Northern celestial hemisphere. The HD 219134 system is a multi-planet architecture hosting 6 confirmed worlds, with HD 219134 g sharing its stellar neighborhood alongside HD 219134 b, HD 219134 c, HD 219134 f, HD 219134 d, HD 219134 h.
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 219134 |
| Spectral Type | K3 V |
| Effective Temp (Teff) | 4,913 K |
| Stellar Radius | 0.7700 R☉ |
| Stellar Mass | 0.7940 M☉ |
| Bolometric Luminosity | 0.31 L☉ |
| Metallicity [Fe/H] | 0.080 dex |
| Stellar Age | 12.460 Gyr |
| Apparent Magnitude | V: 5.569 · G: 5.240 |
| System Architecture | 1 Star, 6 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.375300 AU |
| Orbital Period | 94.2 days |
| Mean Orbital Velocity | 43.3 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.69 g/cm³ (20.3 km/s vesc) |
| Insolation Flux | 2.2009 S⊕ (~2,995 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 21.300 LY (6.531 pc) |