HD 30856 b
Astrophysical Synthesis & Habitability Characterization
HD 30856 b is a confirmed gas giant exoplanet orbiting the star HD 30856, located approximately 427.9 light-years (131.2 parsecs) from the Solar System. First announced in 2011 by W. M. Keck Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13.5 Earth radii (1.2 Jupiter radii) and has a measured mass of 491.683 Earth masses (1.55 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.1 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 2.7 g⊕ (26.48 m/s²), and an escape velocity of 67.5 km/s.
In its orbital architecture around HD 30856, HD 30856 b completes one full revolution every 847 Earth days (2.32Julian years) at a semi-major axis of 1.85 AU (corresponding to the middle-system regime between Mars at 1.52 AU and Jupiter at 5.20 AU). Its mean orbital velocity is approximately 23.8 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.061 carries the world between 1.7372 AU at periapsis and 1.9629 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 364 K (+91°C / +196°F) and receiving 2.89 S⊕ (~3,937 W/m²), HD 30856 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 30856 is classified as an orange K-type star of spectral type K0 III with an effective photospheric temperature of 4,895 K, a radius of 4.4 R☉, a mass of 1.17 M☉, an estimated bolometric luminosity of 9.973 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.8 Gyr and a metallicity of [Fe/H] = -0.06 dex (near-solar heavy-element abundance). From Earth, HD 30856 shines at apparent V-band magnitude 7.91 (accessible to binoculars and small amateur telescopes) in the Southern 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: W. M. Keck Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 30856 |
| Spectral Type | K0 III |
| Effective Temp (Teff) | 4,895 K |
| Stellar Radius | 4.4000 R☉ |
| Stellar Mass | 1.1700 M☉ |
| Bolometric Luminosity | 9.973 L☉ |
| Metallicity [Fe/H] | -0.060 dex |
| Stellar Age | 3.800 Gyr |
| Apparent Magnitude | V: 7.910 · G: 7.658 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.850000 AU |
| Orbital Period | 847 days |
| Mean Orbital Velocity | 23.8 km/s |
| Orbital Eccentricity (e) | 0.06100 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.1 g/cm³ (67.5 km/s vesc) |
| Insolation Flux | 2.8926 S⊕ (~3,937 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 427.900 LY (131.199 pc) |