WASP-31 b
Astrophysical Synthesis & Habitability Characterization
WASP-31 b is a confirmed gas giant exoplanet orbiting the star WASP-31, located approximately 1251.9 light-years (383.83 parsecs) from the Solar System. First announced in 2010 by SuperWASP using the Transit detection technique (producing an estimated primary transit depth of 1.6165% across the stellar disk), this world measures 17.363 Earth radii (1.55 Jupiter radii) and has a measured mass of 151.916 Earth masses (0.48 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.16 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.5 g⊕ (4.9 m/s²), and an escape velocity of 33.1 km/s.
In its orbital architecture around WASP-31, WASP-31 b completes one full revolution every 3.406 Earth days at a semi-major axis of 0.04659 AU (an ultra-close orbit less than one-seventh of Mercury's 0.387 AU distance from the Sun, where strong stellar tidal forces typically induce synchronous rotation). Its mean orbital velocity is approximately 148.8 km/s (compared to Earth's 29.8 km/s). The orbit is modeled as circular (e = 0.00), maintaining a constant stellar distance throughout its year.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1424 K (+1151°C / +2104°F) and receiving 970.94 S⊕ (~1,321,452 W/m²), WASP-31 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star WASP-31 is classified as a stellar host with an effective photospheric temperature of 6,302 K, a radius of 1.252 R☉, a mass of 1.163 M☉, an estimated bolometric luminosity of 2.218 L☉. Stellar evolution modeling indicates an estimated stellar age of 1 Gyr and a metallicity of [Fe/H] = -0.2 dex (metal-poor relative to the Sun). From Earth, WASP-31 shines at apparent V-band magnitude 11.658 (faint and requiring research-grade or CCD telescopic photometry) 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: SuperWASP · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | WASP-31 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 6,302 K |
| Stellar Radius | 1.2520 R☉ |
| Stellar Mass | 1.1630 M☉ |
| Bolometric Luminosity | 2.218 L☉ |
| Metallicity [Fe/H] | -0.200 dex |
| Stellar Age | 1.000 Gyr |
| Apparent Magnitude | V: 11.658 · G: 11.816 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.046590 AU |
| Orbital Period | 3.406 days |
| Mean Orbital Velocity | 148.8 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 84.4100° |
| Mean Bulk Density | 0.16 g/cm³ (33.1 km/s vesc) |
| Insolation Flux | 970.9417 S⊕ (~1,321,452 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1251.900 LY (383.829 pc) |