HD 80606 b
Astrophysical Synthesis & Habitability Characterization
HD 80606 b is a confirmed gas giant exoplanet orbiting the star HD 80606, located approximately 216.8 light-years (66.47 parsecs) from the Solar System. First announced in 2001 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 11.568 Earth radii (1.03 Jupiter radii) and has a measured mass of 1323.469 Earth masses (4.16 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 9.89 g⊕ (96.99 m/s²), and an escape velocity of 119.6 km/s.
In its orbital architecture around HD 80606, HD 80606 b completes one full revolution every 111.437 Earth days at a semi-major axis of 0.4603 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 44.9 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.93183, swinging from 0.0314 AU at periapsis out to 0.8892 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 405 K (+132°C / +270°F) and receiving 4.69 S⊕ (~6,389 W/m²), HD 80606 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 80606 is classified as a solar-type yellow star of spectral type G5 with an effective photospheric temperature of 5,565 K, a radius of 1.05 R☉, a mass of 1.05 M☉, an estimated bolometric luminosity of 0.949 L☉. Stellar evolution modeling indicates an estimated stellar age of 5.9 Gyr and a metallicity of [Fe/H] = 0.35 dex (metal-rich relative to the Sun). From Earth, HD 80606 shines at apparent V-band magnitude 9.06 (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: Multiple Observatories · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 80606 |
| Spectral Type | G5 |
| Effective Temp (Teff) | 5,565 K |
| Stellar Radius | 1.0500 R☉ |
| Stellar Mass | 1.0500 M☉ |
| Bolometric Luminosity | 0.949 L☉ |
| Metallicity [Fe/H] | 0.350 dex |
| Stellar Age | 5.900 Gyr |
| Apparent Magnitude | V: 9.060 · G: 8.820 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.460300 AU |
| Orbital Period | 111.437 days |
| Mean Orbital Velocity | 44.9 km/s |
| Orbital Eccentricity (e) | 0.93183 |
| Orbital Inclination (i) | 89.2400° |
| Mean Bulk Density | 4.71 g/cm³ (119.6 km/s vesc) |
| Insolation Flux | 4.6941 S⊕ (~6,389 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 216.800 LY (66.471 pc) |