HD 219828 c
Astrophysical Synthesis & Habitability Characterization
HD 219828 c is a confirmed gas giant exoplanet orbiting the star HD 219828, located approximately 238.5 light-years (73.11 parsecs) from the Solar System. First announced in 2016 by Multiple Facilities using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 12.2 Earth radii (1.09 Jupiter radii) and has a measured mass of 5102.417 Earth masses (16.05 Jupiter masses). Combining its mass and radius yields a mean bulk density of 15.49 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 34.28 g⊕ (336.17 m/s²), and an escape velocity of 228.8 km/s.
In its orbital architecture around HD 219828, HD 219828 c completes one full revolution every 4789.873 Earth days (13.11Julian years) at a semi-major axis of 5.657 AU (a wide outer-system orbit beyond Jupiter's 5.20 AU distance in our Solar System). Its mean orbital velocity is approximately 12.8 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.811, swinging from 1.0692 AU at periapsis out to 10.2448 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 149 K (-124°C / -191°F) and an incident flux of 0.08 S⊕ (~112 W/m²), surface water and volatile species on HD 219828 c would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star HD 219828 is classified as a solar-type yellow star of spectral type G0 IV with an effective photospheric temperature of 5,891 K, a radius of 1.56 R☉, a mass of 1.04 M☉, an estimated bolometric luminosity of 2.63 L☉. Stellar evolution modeling indicates an estimated stellar age of 5.69 Gyr and a metallicity of [Fe/H] = 0.19 dex (metal-rich relative to the Sun). From Earth, HD 219828 shines at apparent V-band magnitude 8.04 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere. The HD 219828 system is a multi-planet architecture hosting 2 confirmed worlds, with HD 219828 c sharing its stellar neighborhood alongside HD 219828 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: Multiple Facilities · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 219828 |
| Spectral Type | G0 IV |
| Effective Temp (Teff) | 5,891 K |
| Stellar Radius | 1.5600 R☉ |
| Stellar Mass | 1.0400 M☉ |
| Bolometric Luminosity | 2.63 L☉ |
| Metallicity [Fe/H] | 0.190 dex |
| Stellar Age | 5.690 Gyr |
| Apparent Magnitude | V: 8.040 · G: 7.883 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 5.657000 AU |
| Orbital Period | 4789.873 days |
| Mean Orbital Velocity | 12.8 km/s |
| Orbital Eccentricity (e) | 0.81100 |
| Orbital Inclination (i) | 122.8160° |
| Mean Bulk Density | 15.49 g/cm³ (228.8 km/s vesc) |
| Insolation Flux | 0.0822 S⊕ (~112 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 238.500 LY (73.114 pc) |