HD 164604 c
Astrophysical Synthesis & Habitability Characterization
HD 164604 c is a confirmed gas giant exoplanet orbiting the star HD 164604, located approximately 128.4 light-years (39.36 parsecs) from the Solar System. First announced in 2026 by Las Campanas Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 12.5 Earth radii (1.12 Jupiter radii) and has a measured mass of 3019.37 Earth masses (9.5 Jupiter masses). Combining its mass and radius yields a mean bulk density of 8.52 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 19.32 g⊕ (189.46 m/s²), and an escape velocity of 173.9 km/s.
In its orbital architecture around HD 164604, HD 164604 c completes one full revolution every 5387 Earth days (14.75Julian years) at a semi-major axis of 5.556 AU (a wide outer-system orbit beyond Jupiter's 5.20 AU distance in our Solar System). Its mean orbital velocity is approximately 11.2 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.196 carries the world between 4.467 AU at periapsis and 6.645 AU at apoapsis, driving measurable seasonal insolation cycles.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 84 K (-189°C / -308°F) and an incident flux of 0.01 S⊕ (~11 W/m²), surface water and volatile species on HD 164604 c would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star HD 164604 is classified as an orange K-type star of spectral type K3.5 V with an effective photospheric temperature of 4,663 K, a radius of 0.78 R☉, a mass of 0.77 M☉, an estimated bolometric luminosity of 0.258 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.6 Gyr and a metallicity of [Fe/H] = 0.12 dex (metal-rich relative to the Sun). From Earth, HD 164604 shines at apparent V-band magnitude 9.62 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere. The HD 164604 system is a multi-planet architecture hosting 2 confirmed worlds, with HD 164604 c sharing its stellar neighborhood alongside HD 164604 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: Las Campanas Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 164604 |
| Spectral Type | K3.5 V |
| Effective Temp (Teff) | 4,663 K |
| Stellar Radius | 0.7800 R☉ |
| Stellar Mass | 0.7700 M☉ |
| Bolometric Luminosity | 0.258 L☉ |
| Metallicity [Fe/H] | 0.120 dex |
| Stellar Age | 1.600 Gyr |
| Apparent Magnitude | V: 9.620 · G: 9.328 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 5.556000 AU |
| Orbital Period | 5387 days |
| Mean Orbital Velocity | 11.2 km/s |
| Orbital Eccentricity (e) | 0.19600 |
| Orbital Inclination (i) | 8.6000° |
| Mean Bulk Density | 8.52 g/cm³ (173.9 km/s vesc) |
| Insolation Flux | 0.0084 S⊕ (~11 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 128.400 LY (39.363 pc) |