HD 40956 b
Astrophysical Synthesis & Habitability Characterization
HD 40956 b is a confirmed gas giant exoplanet orbiting the star HD 40956, located approximately 380.3 light-years (116.59 parsecs) from the Solar System. First announced in 2017 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13.2 Earth radii (1.18 Jupiter radii) and has a measured mass of 858.141 Earth masses (2.7 Jupiter masses). Combining its mass and radius yields a mean bulk density of 2.06 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 4.93 g⊕ (48.35 m/s²), and an escape velocity of 90.2 km/s.
In its orbital architecture around HD 40956, HD 40956 b completes one full revolution every 578.6 Earth days (1.58Julian years) at a semi-major axis of 1.4 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 26.3 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.24 carries the world between 1.064 AU at periapsis and 1.736 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 581 K (+308°C / +586°F) and receiving 23.56 S⊕ (~32,060 W/m²), HD 40956 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 40956 is classified as an orange K-type star of spectral type K0 with an effective photospheric temperature of 4,869 K, a radius of 8.56 R☉, a mass of 2 M☉, an estimated bolometric luminosity of 36.948 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.35 Gyr and a metallicity of [Fe/H] = 0.14 dex (metal-rich relative to the Sun). From Earth, HD 40956 shines at apparent V-band magnitude 6.428 (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 40956 |
| Spectral Type | K0 |
| Effective Temp (Teff) | 4,869 K |
| Stellar Radius | 8.5600 R☉ |
| Stellar Mass | 2.0000 M☉ |
| Bolometric Luminosity | 36.948 L☉ |
| Metallicity [Fe/H] | 0.140 dex |
| Stellar Age | 1.350 Gyr |
| Apparent Magnitude | V: 6.428 · G: 6.140 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.400000 AU |
| Orbital Period | 578.6 days |
| Mean Orbital Velocity | 26.3 km/s |
| Orbital Eccentricity (e) | 0.24000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 2.06 g/cm³ (90.2 km/s vesc) |
| Insolation Flux | 23.5561 S⊕ (~32,060 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 380.300 LY (116.593 pc) |