HD 219134 d
Astrophysical Synthesis & Habitability Characterization
HD 219134 d is a confirmed super-earth exoplanet orbiting the star HD 219134, located approximately 21.3 light-years (6.53 parsecs) from the Solar System. First announced in 2015 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 1.61 Earth radii and has a measured mass of 16.17 Earth masses. Combining its mass and radius yields a mean bulk density of 21.36 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 6.24 g⊕ (61.19 m/s²), and an escape velocity of 35.5 km/s.
In its orbital architecture around HD 219134, HD 219134 d completes one full revolution every 46.859 Earth days at a semi-major axis of 0.237 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 55 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.138 carries the world between 0.2043 AU at periapsis and 0.2697 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 411 K (+138°C / +280°F) and receiving 4.72 S⊕ (~6,424 W/m²), HD 219134 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 219134 is classified as an orange K-type star of spectral type K3 V with an effective photospheric temperature of 4,699 K, a radius of 0.778 R☉, a mass of 0.81 M☉, an estimated bolometric luminosity of 0.265 L☉. Stellar evolution modeling indicates an estimated stellar age of 11 Gyr and a metallicity of [Fe/H] = 0.11 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 d sharing its stellar neighborhood alongside HD 219134 b, HD 219134 c, HD 219134 f, HD 219134 g, 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: Roque de los Muchachos Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 219134 |
| Spectral Type | K3 V |
| Effective Temp (Teff) | 4,699 K |
| Stellar Radius | 0.7780 R☉ |
| Stellar Mass | 0.8100 M☉ |
| Bolometric Luminosity | 0.265 L☉ |
| Metallicity [Fe/H] | 0.110 dex |
| Stellar Age | 11.000 Gyr |
| Apparent Magnitude | V: 5.569 · G: 5.240 |
| System Architecture | 1 Star, 6 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.237000 AU |
| Orbital Period | 46.859 days |
| Mean Orbital Velocity | 55 km/s |
| Orbital Eccentricity (e) | 0.13800 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 21.36 g/cm³ (35.5 km/s vesc) |
| Insolation Flux | 4.7200 S⊕ (~6,424 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 21.300 LY (6.531 pc) |