HD 181433 d
Astrophysical Synthesis & Habitability Characterization
HD 181433 d is a confirmed gas giant exoplanet orbiting the star HD 181433, located approximately 87.7 light-years (26.88 parsecs) from the Solar System. First announced in 2008 by La Silla 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 858.137 Earth masses (2.7 Jupiter masses). Combining its mass and radius yields a mean bulk density of 2.06 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 4.93 g⊕ (48.35 m/s²), and an escape velocity of 90.2 km/s.
In its orbital architecture around HD 181433, HD 181433 d completes one full revolution every 6896.1 Earth days (18.88Julian years) at a semi-major axis of 6.74 AU (a wide outer-system orbit beyond Jupiter's 5.20 AU distance in our Solar System). Its mean orbital velocity is approximately 10.6 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.444, swinging from 3.7474 AU at periapsis out to 9.7326 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 81 K (-192°C / -314°F) and an incident flux of 0.01 S⊕ (~10 W/m²), surface water and volatile species on HD 181433 d would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star HD 181433 is classified as an orange K-type star of spectral type K3 IV with an effective photospheric temperature of 4,918 K, a radius of 0.79 R☉, a mass of 0.86 M☉, an estimated bolometric luminosity of 0.328 L☉. Stellar evolution modeling indicates an estimated stellar age of 6.7 Gyr and a metallicity of [Fe/H] = 0.401 dex (metal-rich relative to the Sun). From Earth, HD 181433 shines at apparent V-band magnitude 8.4 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere. The HD 181433 system is a multi-planet architecture hosting 3 confirmed worlds, with HD 181433 d sharing its stellar neighborhood alongside HD 181433 b, HD 181433 c.
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 181433 |
| Spectral Type | K3 IV |
| Effective Temp (Teff) | 4,918 K |
| Stellar Radius | 0.7900 R☉ |
| Stellar Mass | 0.8600 M☉ |
| Bolometric Luminosity | 0.328 L☉ |
| Metallicity [Fe/H] | 0.401 dex |
| Stellar Age | 6.700 Gyr |
| Apparent Magnitude | V: 8.400 · G: 8.092 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 6.740000 AU |
| Orbital Period | 6896.1 days |
| Mean Orbital Velocity | 10.6 km/s |
| Orbital Eccentricity (e) | 0.44400 |
| Orbital Inclination (i) | 164.5000° |
| Mean Bulk Density | 2.06 g/cm³ (90.2 km/s vesc) |
| Insolation Flux | 0.0077 S⊕ (~10 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 87.700 LY (26.876 pc) |