HD 204313 b
Astrophysical Synthesis & Habitability Characterization
HD 204313 b is a confirmed gas giant exoplanet orbiting the star HD 204313, located approximately 155.9 light-years (47.8 parsecs) from the Solar System. First announced in 2010 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 12.9 Earth radii (1.15 Jupiter radii) and has a measured mass of 1466.778 Earth masses (4.61 Jupiter masses). Combining its mass and radius yields a mean bulk density of 3.77 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 8.81 g⊕ (86.4 m/s²), and an escape velocity of 119.3 km/s.
In its orbital architecture around HD 204313, HD 204313 b completes one full revolution every 2041.115 Earth days (5.59Julian years) at a semi-major axis of 3.185 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 17 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.1 carries the world between 2.8665 AU at periapsis and 3.5035 AU at apoapsis, driving measurable seasonal insolation cycles.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 163 K (-110°C / -166°F) and an incident flux of 0.12 S⊕ (~169 W/m²), surface water and volatile species on HD 204313 b would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star HD 204313 is classified as a solar-type yellow star of spectral type G5 V with an effective photospheric temperature of 5,767 K, a radius of 1.1 R☉, a mass of 1.03 M☉, an estimated bolometric luminosity of 1.201 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.38 Gyr and a metallicity of [Fe/H] = 0.18 dex (metal-rich relative to the Sun). From Earth, HD 204313 shines at apparent V-band magnitude 7.99 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere. The HD 204313 system is a multi-planet architecture hosting 3 confirmed worlds, with HD 204313 b sharing its stellar neighborhood alongside HD 204313 c, HD 204313 e.
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 204313 |
| Spectral Type | G5 V |
| Effective Temp (Teff) | 5,767 K |
| Stellar Radius | 1.1000 R☉ |
| Stellar Mass | 1.0300 M☉ |
| Bolometric Luminosity | 1.201 L☉ |
| Metallicity [Fe/H] | 0.180 dex |
| Stellar Age | 3.380 Gyr |
| Apparent Magnitude | V: 7.990 · G: 7.832 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 3.185000 AU |
| Orbital Period | 2041.115 days |
| Mean Orbital Velocity | 17 km/s |
| Orbital Eccentricity (e) | 0.10000 |
| Orbital Inclination (i) | 72.9170° |
| Mean Bulk Density | 3.77 g/cm³ (119.3 km/s vesc) |
| Insolation Flux | 0.1240 S⊕ (~169 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 155.900 LY (47.795 pc) |