HD 3651 b
Astrophysical Synthesis & Habitability Characterization
HD 3651 b is a confirmed gas giant exoplanet orbiting the star HD 3651, located approximately 36.3 light-years (11.13 parsecs) from the Solar System. First announced in 2003 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 10.1 Earth radii (0.9 Jupiter radii) and has a measured mass of 72.465 Earth masses (0.23 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.39 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.71 g⊕ (6.96 m/s²), and an escape velocity of 30 km/s.
In its orbital architecture around HD 3651, HD 3651 b completes one full revolution every 62.25 Earth days at a semi-major axis of 0.295 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 51.6 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.645, swinging from 0.1047 AU at periapsis out to 0.4853 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 433 K (+160°C / +320°F) and receiving 6.11 S⊕ (~8,319 W/m²), HD 3651 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 3651 is classified as an orange K-type star of spectral type K0 V with an effective photospheric temperature of 5,221 K, a radius of 0.872 R☉, a mass of 0.799 M☉, an estimated bolometric luminosity of 0.507 L☉. Stellar evolution modeling indicates an estimated stellar age of 3 Gyr and a metallicity of [Fe/H] = 0.145 dex (metal-rich relative to the Sun). From Earth, HD 3651 shines at apparent V-band magnitude 5.884 (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: Multiple Observatories · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 3651 |
| Spectral Type | K0 V |
| Effective Temp (Teff) | 5,221 K |
| Stellar Radius | 0.8720 R☉ |
| Stellar Mass | 0.7990 M☉ |
| Bolometric Luminosity | 0.507 L☉ |
| Metallicity [Fe/H] | 0.145 dex |
| Stellar Age | 3.000 Gyr |
| Apparent Magnitude | V: 5.884 · G: 5.653 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.295000 AU |
| Orbital Period | 62.25 days |
| Mean Orbital Velocity | 51.6 km/s |
| Orbital Eccentricity (e) | 0.64500 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.39 g/cm³ (30 km/s vesc) |
| Insolation Flux | 6.1123 S⊕ (~8,319 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 36.300 LY (11.134 pc) |