HD 165131 b
Astrophysical Synthesis & Habitability Characterization
HD 165131 b is a confirmed gas giant exoplanet orbiting the star HD 165131, located approximately 187.3 light-years (57.43 parsecs) from the Solar System. First announced in 2023 by Multiple Facilities using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 12.1 Earth radii (1.08 Jupiter radii) and has a measured mass of 5943.391 Earth masses (18.7 Jupiter masses). Combining its mass and radius yields a mean bulk density of 18.5 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 40.59 g⊕ (398.05 m/s²), and an escape velocity of 247.9 km/s.
In its orbital architecture around HD 165131, HD 165131 b completes one full revolution every 2342.6 Earth days (6.41Julian years) at a semi-major axis of 3.54 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 16.4 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.6708, swinging from 1.1654 AU at periapsis out to 5.9146 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 155 K (-118°C / -180°F) and an incident flux of 0.10 S⊕ (~132 W/m²), surface water and volatile species on HD 165131 b would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star HD 165131 is classified as a solar-type yellow star of spectral type G3/5 V with an effective photospheric temperature of 5,870 K, a radius of 1.0642 R☉, a mass of 1.06 M☉, an estimated bolometric luminosity of 1.206 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.7 Gyr and a metallicity of [Fe/H] = 0.06 dex (metal-rich relative to the Sun). From Earth, HD 165131 shines at apparent V-band magnitude 8.42 (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: Multiple Facilities · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 165131 |
| Spectral Type | G3/5 V |
| Effective Temp (Teff) | 5,870 K |
| Stellar Radius | 1.0642 R☉ |
| Stellar Mass | 1.0600 M☉ |
| Bolometric Luminosity | 1.206 L☉ |
| Metallicity [Fe/H] | 0.060 dex |
| Stellar Age | 2.700 Gyr |
| Apparent Magnitude | V: 8.420 · G: 8.261 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 3.540000 AU |
| Orbital Period | 2342.6 days |
| Mean Orbital Velocity | 16.4 km/s |
| Orbital Eccentricity (e) | 0.67080 |
| Orbital Inclination (i) | 70.0000° |
| Mean Bulk Density | 18.5 g/cm³ (247.9 km/s vesc) |
| Insolation Flux | 0.0967 S⊕ (~132 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 187.300 LY (57.426 pc) |