HD 28185 b
Astrophysical Synthesis & Habitability Characterization
HD 28185 b is a confirmed gas giant exoplanet orbiting the star HD 28185, located approximately 128.4 light-years (39.38 parsecs) from the Solar System. First announced in 2001 by La Silla 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 1859.296 Earth masses (5.85 Jupiter masses). Combining its mass and radius yields a mean bulk density of 4.89 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 11.35 g⊕ (111.31 m/s²), and an escape velocity of 134.8 km/s.
In its orbital architecture around HD 28185, HD 28185 b completes one full revolution every 385.92 Earth days (1.06Julian years) at a semi-major axis of 1.034 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 29.1 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.063 carries the world between 0.9689 AU at periapsis and 1.0991 AU at apoapsis, driving measurable seasonal insolation cycles.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 12.800 R⊕, HD 28185 b exceeds the empirical ~1.8–2.2 R⊕ Fulton radius valley threshold, indicating a substantial hydrogen-helium or supercritical volatile envelope without a conventional solid terrestrial surface.
The host star HD 28185 is classified as a solar-type yellow star of spectral type G5 with an effective photospheric temperature of 5,602 K, a radius of 1.048 R☉, a mass of 0.974 M☉, an estimated bolometric luminosity of 0.97 L☉. Stellar evolution modeling indicates an estimated stellar age of 8.3 Gyr and a metallicity of [Fe/H] = 0.19 dex (metal-rich relative to the Sun). From Earth, HD 28185 shines at apparent V-band magnitude 7.8 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere. The HD 28185 system is a multi-planet architecture hosting 2 confirmed worlds, with HD 28185 b sharing its stellar neighborhood alongside HD 28185 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: La Silla Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 28185 |
| Spectral Type | G5 |
| Effective Temp (Teff) | 5,602 K |
| Stellar Radius | 1.0480 R☉ |
| Stellar Mass | 0.9740 M☉ |
| Bolometric Luminosity | 0.97 L☉ |
| Metallicity [Fe/H] | 0.190 dex |
| Stellar Age | 8.300 Gyr |
| Apparent Magnitude | V: 7.800 · G: 7.627 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.034000 AU |
| Orbital Period | 385.92 days |
| Mean Orbital Velocity | 29.1 km/s |
| Orbital Eccentricity (e) | 0.06300 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 4.89 g/cm³ (134.8 km/s vesc) |
| Insolation Flux | 0.9073 S⊕ (~1,235 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 128.400 LY (39.381 pc) |