HD 79181 b
Astrophysical Synthesis & Habitability Characterization
HD 79181 b is a confirmed gas giant exoplanet orbiting the star HD 79181, located approximately 337 light-years (103.34 parsecs) from the Solar System. First announced in 2021 by Okayama Astrophysical Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 14.1 Earth radii (1.26 Jupiter radii) and has a measured mass of 203.41 Earth masses (0.64 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.4 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.02 g⊕ (10 m/s²), and an escape velocity of 42.5 km/s.
In its orbital architecture around HD 79181, HD 79181 b completes one full revolution every 273.1 Earth days at a semi-major axis of 0.9 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 35.9 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.259, swinging from 0.6669 AU at periapsis out to 1.1331 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 822 K (+549°C / +1020°F) and receiving 76.06 S⊕ (~103,520 W/m²), HD 79181 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 79181 is classified as a solar-type yellow star of spectral type G8 III with an effective photospheric temperature of 4,862 K, a radius of 11.06 R☉, a mass of 1.28 M☉, an estimated bolometric luminosity of 61.328 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.28 dex (metal-poor relative to the Sun). From Earth, HD 79181 shines at apparent V-band magnitude 5.72 (visible to the unaided human eye under dark skies) 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: Okayama Astrophysical Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 79181 |
| Spectral Type | G8 III |
| Effective Temp (Teff) | 4,862 K |
| Stellar Radius | 11.0600 R☉ |
| Stellar Mass | 1.2800 M☉ |
| Bolometric Luminosity | 61.328 L☉ |
| Metallicity [Fe/H] | -0.280 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 5.720 · G: 5.453 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.900000 AU |
| Orbital Period | 273.1 days |
| Mean Orbital Velocity | 35.9 km/s |
| Orbital Eccentricity (e) | 0.25900 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.4 g/cm³ (42.5 km/s vesc) |
| Insolation Flux | 76.0617 S⊕ (~103,520 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 337.000 LY (103.335 pc) |