HD 80869 b
Astrophysical Synthesis & Habitability Characterization
HD 80869 b is a confirmed gas giant exoplanet orbiting the star HD 80869, located approximately 278.5 light-years (85.4 parsecs) from the Solar System. First announced in 2021 by Haute-Provence 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 1609.801 Earth masses (5.06 Jupiter masses). Combining its mass and radius yields a mean bulk density of 4.23 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 9.83 g⊕ (96.4 m/s²), and an escape velocity of 125.4 km/s.
In its orbital architecture around HD 80869, HD 80869 b completes one full revolution every 1752.921 Earth days (4.8Julian years) at a semi-major axis of 2.905 AU (corresponding to the middle-system regime between Mars at 1.52 AU and Jupiter at 5.20 AU). Its mean orbital velocity is approximately 18 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.924, swinging from 0.2208 AU at periapsis out to 5.5892 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 12.800 R⊕, HD 80869 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 80869 is classified as a solar-type yellow star of spectral type G5 with an effective photospheric temperature of 5,837 K, a radius of 1.062 R☉, a mass of 1.06 M☉, an estimated bolometric luminosity of 1.175 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.17 dex (metal-rich relative to the Sun). From Earth, HD 80869 shines at apparent V-band magnitude 8.48 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere.
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: Haute-Provence Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 80869 |
| Spectral Type | G5 |
| Effective Temp (Teff) | 5,837 K |
| Stellar Radius | 1.0620 R☉ |
| Stellar Mass | 1.0600 M☉ |
| Bolometric Luminosity | 1.175 L☉ |
| Metallicity [Fe/H] | 0.170 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 8.480 · G: 8.332 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 2.905000 AU |
| Orbital Period | 1752.921 days |
| Mean Orbital Velocity | 18 km/s |
| Orbital Eccentricity (e) | 0.92400 |
| Orbital Inclination (i) | 98.5590° |
| Mean Bulk Density | 4.23 g/cm³ (125.4 km/s vesc) |
| Insolation Flux | 0.1420 S⊕ (~193 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 278.500 LY (85.395 pc) |