HD 40979 b
Astrophysical Synthesis & Habitability Characterization
HD 40979 b is a confirmed gas giant exoplanet orbiting the star HD 40979, located approximately 111.2 light-years (34.09 parsecs) from the Solar System. First announced in 2002 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 12.9 Earth radii (1.15 Jupiter radii) and has a measured mass of 1484.266 Earth masses (4.67 Jupiter masses). Combining its mass and radius yields a mean bulk density of 3.81 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 8.92 g⊕ (87.48 m/s²), and an escape velocity of 120 km/s.
In its orbital architecture around HD 40979, HD 40979 b completes one full revolution every 264.15 Earth days at a semi-major axis of 0.85 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 35 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.25, swinging from 0.6375 AU at periapsis out to 1.0625 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 355 K (+82°C / +180°F) and receiving 2.70 S⊕ (~3,678 W/m²), HD 40979 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 40979 is classified as a warm F-type star of spectral type F8 V with an effective photospheric temperature of 6,165 K, a radius of 1.21 R☉, a mass of 1.45 M☉, an estimated bolometric luminosity of 1.898 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.56 Gyr and a metallicity of [Fe/H] = 0.2 dex (metal-rich relative to the Sun). From Earth, HD 40979 shines at apparent V-band magnitude 6.755 (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 40979 |
| Spectral Type | F8 V |
| Effective Temp (Teff) | 6,165 K |
| Stellar Radius | 1.2100 R☉ |
| Stellar Mass | 1.4500 M☉ |
| Bolometric Luminosity | 1.898 L☉ |
| Metallicity [Fe/H] | 0.200 dex |
| Stellar Age | 3.560 Gyr |
| Apparent Magnitude | V: 6.755 · G: 6.600 |
| System Architecture | 3 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.850000 AU |
| Orbital Period | 264.15 days |
| Mean Orbital Velocity | 35 km/s |
| Orbital Eccentricity (e) | 0.25000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 3.81 g/cm³ (120 km/s vesc) |
| Insolation Flux | 2.7022 S⊕ (~3,678 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 111.200 LY (34.088 pc) |