HD 75784 c
Astrophysical Synthesis & Habitability Characterization
HD 75784 c is a confirmed gas giant exoplanet orbiting the star HD 75784, located approximately 278.6 light-years (85.43 parsecs) from the Solar System. First announced in 2018 by W. M. Keck Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 12.8 Earth radii (1.14 Jupiter radii) and has a measured mass of 1792.561 Earth masses (5.64 Jupiter masses). Combining its mass and radius yields a mean bulk density of 4.71 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 10.94 g⊕ (107.28 m/s²), and an escape velocity of 132.4 km/s.
In its orbital architecture around HD 75784, HD 75784 c completes one full revolution every 7900 Earth days (21.63Julian years) at a semi-major axis of 8.4 AU (a wide outer-system orbit beyond Jupiter's 5.20 AU distance in our Solar System). Its mean orbital velocity is approximately 11.6 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.489, swinging from 4.2924 AU at periapsis out to 12.5076 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⊕ (~110 W/m²), surface water and volatile species on HD 75784 c would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star HD 75784 is classified as a solar-type yellow star of spectral type G5 with an effective photospheric temperature of 4,867 K, a radius of 3.4 R☉, a mass of 1.26 M☉, an estimated bolometric luminosity of 5.82 L☉. Stellar evolution modeling indicates an estimated stellar age of 4 Gyr and a metallicity of [Fe/H] = 0.25 dex (metal-rich relative to the Sun). From Earth, HD 75784 shines at apparent V-band magnitude 7.84 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere. The HD 75784 system is a multi-planet architecture hosting 2 confirmed worlds, with HD 75784 c sharing its stellar neighborhood alongside HD 75784 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: W. M. Keck Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 75784 |
| Spectral Type | G5 |
| Effective Temp (Teff) | 4,867 K |
| Stellar Radius | 3.4000 R☉ |
| Stellar Mass | 1.2600 M☉ |
| Bolometric Luminosity | 5.82 L☉ |
| Metallicity [Fe/H] | 0.250 dex |
| Stellar Age | 4.000 Gyr |
| Apparent Magnitude | V: 7.840 · G: 7.560 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 8.400000 AU |
| Orbital Period | 7900 days |
| Mean Orbital Velocity | 11.6 km/s |
| Orbital Eccentricity (e) | 0.48900 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 4.71 g/cm³ (132.4 km/s vesc) |
| Insolation Flux | 0.0808 S⊕ (~110 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 278.600 LY (85.432 pc) |