HD 59686 A b
Astrophysical Synthesis & Habitability Characterization
HD 59686 A b is a confirmed gas giant exoplanet orbiting the star HD 59686 A, located approximately 291.2 light-years (89.27 parsecs) from the Solar System. First announced in 2016 by Lick Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 12.7 Earth radii (1.13 Jupiter radii) and has a measured mass of 2199.384 Earth masses (6.92 Jupiter masses). Combining its mass and radius yields a mean bulk density of 5.92 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 13.64 g⊕ (133.76 m/s²), and an escape velocity of 147.2 km/s.
In its orbital architecture around HD 59686 A, HD 59686 A b completes one full revolution every 299.36 Earth days at a semi-major axis of 1.086 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 39.5 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.05 carries the world between 1.0317 AU at periapsis and 1.1403 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 783 K (+510°C / +950°F) and receiving 56.23 S⊕ (~76,534 W/m²), HD 59686 A b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 59686 A is classified as an orange K-type star of spectral type K2 III with an effective photospheric temperature of 4,658 K, a radius of 13.2 R☉, a mass of 1.9 M☉, an estimated bolometric luminosity of 73.593 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.73 Gyr and a metallicity of [Fe/H] = 0.15 dex (metal-rich relative to the Sun). From Earth, HD 59686 A shines at apparent V-band magnitude 5.443 (visible to the unaided human eye under dark skies) 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: Lick Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 59686 A |
| Spectral Type | K2 III |
| Effective Temp (Teff) | 4,658 K |
| Stellar Radius | 13.2000 R☉ |
| Stellar Mass | 1.9000 M☉ |
| Bolometric Luminosity | 73.593 L☉ |
| Metallicity [Fe/H] | 0.150 dex |
| Stellar Age | 1.730 Gyr |
| Apparent Magnitude | V: 5.443 · G: 5.132 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.086000 AU |
| Orbital Period | 299.36 days |
| Mean Orbital Velocity | 39.5 km/s |
| Orbital Eccentricity (e) | 0.05000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 5.92 g/cm³ (147.2 km/s vesc) |
| Insolation Flux | 56.2338 S⊕ (~76,534 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 291.200 LY (89.272 pc) |