HD 75784 b
Astrophysical Synthesis & Habitability Characterization
HD 75784 b 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 2014 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 13.8 Earth radii (1.23 Jupiter radii) and has a measured mass of 317.83 Earth masses (1 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.67 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.67 g⊕ (16.38 m/s²), and an escape velocity of 53.7 km/s.
In its orbital architecture around HD 75784, HD 75784 b completes one full revolution every 341.2 Earth days at a semi-major axis of 1.032 AU (comparable to the inner terrestrial zone between Venus, Earth at 1.00 AU, and Mars at 1.52 AU). Its mean orbital velocity is approximately 32.9 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.097 carries the world between 0.9319 AU at periapsis and 1.1321 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 426 K (+153°C / +307°F) and receiving 5.35 S⊕ (~7,286 W/m²), HD 75784 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
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 b sharing its stellar neighborhood alongside HD 75784 c.
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) | 1.032000 AU |
| Orbital Period | 341.2 days |
| Mean Orbital Velocity | 32.9 km/s |
| Orbital Eccentricity (e) | 0.09700 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.67 g/cm³ (53.7 km/s vesc) |
| Insolation Flux | 5.3535 S⊕ (~7,286 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 278.600 LY (85.432 pc) |