HD 73256 c
Astrophysical Synthesis & Habitability Characterization
HD 73256 c is a confirmed gas giant exoplanet orbiting the star HD 73256, located approximately 119.7 light-years (36.71 parsecs) from the Solar System. First announced in 2023 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 12.2 Earth radii (1.09 Jupiter radii) and has a measured mass of 5085.255 Earth masses (16 Jupiter masses). Combining its mass and radius yields a mean bulk density of 15.44 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 34.17 g⊕ (335.09 m/s²), and an escape velocity of 228.4 km/s.
In its orbital architecture around HD 73256, HD 73256 c completes one full revolution every 2690 Earth days (7.36Julian years) at a semi-major axis of 3.8 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 15.4 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.16 carries the world between 3.192 AU at periapsis and 4.408 AU at apoapsis, driving measurable seasonal insolation cycles.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 134 K (-139°C / -218°F) and an incident flux of 0.05 S⊕ (~70 W/m²), surface water and volatile species on HD 73256 c would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star HD 73256 is classified as a solar-type yellow star of spectral type G8 IV with an effective photospheric temperature of 5,570 K, a radius of 0.9447 R☉, a mass of 1 M☉, an estimated bolometric luminosity of 0.771 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.2 Gyr and a metallicity of [Fe/H] = 0.29 dex (metal-rich relative to the Sun). From Earth, HD 73256 shines at apparent V-band magnitude 8.08 (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: La Silla Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 73256 |
| Spectral Type | G8 IV |
| Effective Temp (Teff) | 5,570 K |
| Stellar Radius | 0.9447 R☉ |
| Stellar Mass | 1.0000 M☉ |
| Bolometric Luminosity | 0.771 L☉ |
| Metallicity [Fe/H] | 0.290 dex |
| Stellar Age | 2.200 Gyr |
| Apparent Magnitude | V: 8.080 · G: 7.857 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 3.800000 AU |
| Orbital Period | 2690 days |
| Mean Orbital Velocity | 15.4 km/s |
| Orbital Eccentricity (e) | 0.16000 |
| Orbital Inclination (i) | 29.0000° |
| Mean Bulk Density | 15.44 g/cm³ (228.4 km/s vesc) |
| Insolation Flux | 0.0511 S⊕ (~70 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 119.700 LY (36.708 pc) |