HD 4313 b
Astrophysical Synthesis & Habitability Characterization
HD 4313 b is a confirmed gas giant exoplanet orbiting the star HD 4313, located approximately 444.6 light-years (136.31 parsecs) from the Solar System. First announced in 2009 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 13.4 Earth radii (1.2 Jupiter radii) and has a measured mass of 612.458 Earth masses (1.93 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.4 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 3.41 g⊕ (33.44 m/s²), and an escape velocity of 75.6 km/s.
In its orbital architecture around HD 4313, HD 4313 b completes one full revolution every 356.21 Earth days at a semi-major axis of 1.157 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 35.3 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.147 carries the world between 0.9869 AU at periapsis and 1.3271 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 502 K (+229°C / +444°F) and receiving 10.53 S⊕ (~14,335 W/m²), HD 4313 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 4313 is classified as a solar-type yellow star of spectral type G5 with an effective photospheric temperature of 4,943 K, a radius of 5.14 R☉, a mass of 1.63 M☉, an estimated bolometric luminosity of 14.151 L☉. Stellar evolution modeling indicates an estimated stellar age of 2 Gyr and a metallicity of [Fe/H] = 0.14 dex (metal-rich relative to the Sun). From Earth, HD 4313 shines at apparent V-band magnitude 7.83 (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: W. M. Keck Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 4313 |
| Spectral Type | G5 |
| Effective Temp (Teff) | 4,943 K |
| Stellar Radius | 5.1400 R☉ |
| Stellar Mass | 1.6300 M☉ |
| Bolometric Luminosity | 14.151 L☉ |
| Metallicity [Fe/H] | 0.140 dex |
| Stellar Age | 2.000 Gyr |
| Apparent Magnitude | V: 7.830 · G: 7.574 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.157000 AU |
| Orbital Period | 356.21 days |
| Mean Orbital Velocity | 35.3 km/s |
| Orbital Eccentricity (e) | 0.14700 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.4 g/cm³ (75.6 km/s vesc) |
| Insolation Flux | 10.5330 S⊕ (~14,335 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 444.600 LY (136.308 pc) |