HD 133131 B b
Astrophysical Synthesis & Habitability Characterization
HD 133131 B b is a confirmed gas giant exoplanet orbiting the star HD 133131 B, located approximately 167.3 light-years (51.3 parsecs) from the Solar System. First announced in 2016 by Las Campanas Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13.3 Earth radii (1.19 Jupiter radii) and has a measured mass of 794.575 Earth masses (2.5 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.86 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 4.49 g⊕ (44.03 m/s²), and an escape velocity of 86.5 km/s.
In its orbital architecture around HD 133131 B, HD 133131 B b completes one full revolution every 5769 Earth days (15.79Julian years) at a semi-major axis of 6.15 AU (a wide outer-system orbit beyond Jupiter's 5.20 AU distance in our Solar System). Its mean orbital velocity is approximately 11.6 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.61, swinging from 2.3985 AU at periapsis out to 9.9015 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 112 K (-161°C / -258°F) and an incident flux of 0.03 S⊕ (~35 W/m²), surface water and volatile species on HD 133131 B b would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star HD 133131 B is classified as a solar-type yellow star of spectral type G2 V with an effective photospheric temperature of 5,805 K, a radius of 0.9895 R☉, a mass of 0.93 M☉, an estimated bolometric luminosity of 0.998 L☉. Stellar evolution modeling indicates an estimated stellar age of 9.7 Gyr and a metallicity of [Fe/H] = -0.281 dex (metal-poor relative to the Sun). From Earth, HD 133131 B shines at apparent V-band magnitude 8.413 (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: Las Campanas Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 133131 B |
| Spectral Type | G2 V |
| Effective Temp (Teff) | 5,805 K |
| Stellar Radius | 0.9895 R☉ |
| Stellar Mass | 0.9300 M☉ |
| Bolometric Luminosity | 0.998 L☉ |
| Metallicity [Fe/H] | -0.281 dex |
| Stellar Age | 9.700 Gyr |
| Apparent Magnitude | V: 8.413 · G: 8.257 |
| System Architecture | 2 Stars, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 6.150000 AU |
| Orbital Period | 5769 days |
| Mean Orbital Velocity | 11.6 km/s |
| Orbital Eccentricity (e) | 0.61000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.86 g/cm³ (86.5 km/s vesc) |
| Insolation Flux | 0.0259 S⊕ (~35 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 167.300 LY (51.299 pc) |