HD 181342 b
Astrophysical Synthesis & Habitability Characterization
HD 181342 b is a confirmed gas giant exoplanet orbiting the star HD 181342, located approximately 392.7 light-years (120.39 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 13.2 Earth radii (1.18 Jupiter radii) and has a measured mass of 807.288 Earth masses (2.54 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.94 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 4.63 g⊕ (45.4 m/s²), and an escape velocity of 87.5 km/s.
In its orbital architecture around HD 181342, HD 181342 b completes one full revolution every 564.1 Earth days (1.54Julian years) at a semi-major axis of 1.592 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 30.7 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.022 (ranging from 1.557 AU at periapsis to 1.627 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 410 K (+137°C / +279°F) and receiving 5.84 S⊕ (~7,943 W/m²), HD 181342 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 181342 is classified as an orange K-type star of spectral type K0 III with an effective photospheric temperature of 4,945 K, a radius of 4.71 R☉, a mass of 1.69 M☉, an estimated bolometric luminosity of 11.901 L☉. Stellar evolution modeling indicates an estimated stellar age of 2 Gyr and a metallicity of [Fe/H] = 0.26 dex (metal-rich relative to the Sun). From Earth, HD 181342 shines at apparent V-band magnitude 7.55 (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 181342 |
| Spectral Type | K0 III |
| Effective Temp (Teff) | 4,945 K |
| Stellar Radius | 4.7100 R☉ |
| Stellar Mass | 1.6900 M☉ |
| Bolometric Luminosity | 11.901 L☉ |
| Metallicity [Fe/H] | 0.260 dex |
| Stellar Age | 2.000 Gyr |
| Apparent Magnitude | V: 7.550 · G: 7.284 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.592000 AU |
| Orbital Period | 564.1 days |
| Mean Orbital Velocity | 30.7 km/s |
| Orbital Eccentricity (e) | 0.02200 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.94 g/cm³ (87.5 km/s vesc) |
| Insolation Flux | 5.8360 S⊕ (~7,943 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 392.700 LY (120.391 pc) |