WASP-91 b
Astrophysical Synthesis & Habitability Characterization
WASP-91 b is a confirmed gas giant exoplanet orbiting the star WASP-91, located approximately 489 light-years (149.94 parsecs) from the Solar System. First announced in 2017 by SuperWASP-South using the Transit detection technique (producing an estimated primary transit depth of 1.5147% across the stellar disk), this world measures 11.545 Earth radii (1.03 Jupiter radii) and has a measured mass of 425.892 Earth masses (1.34 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.53 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 3.2 g⊕ (31.38 m/s²), and an escape velocity of 67.9 km/s.
In its orbital architecture around WASP-91, WASP-91 b completes one full revolution every 2.799 Earth days at a semi-major axis of 0.037 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 143.8 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 1160 K (+887°C / +1629°F) and receiving 332.56 S⊕ (~452,609 W/m²), WASP-91 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star WASP-91 is classified as an orange K-type star of spectral type K3 with an effective photospheric temperature of 4,920 K, a radius of 0.86 R☉, a mass of 0.84 M☉, an estimated bolometric luminosity of 0.389 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.19 dex (metal-rich relative to the Sun). From Earth, WASP-91 shines at apparent V-band magnitude 11.98 (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-South · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | WASP-91 |
| Spectral Type | K3 |
| Effective Temp (Teff) | 4,920 K |
| Stellar Radius | 0.8600 R☉ |
| Stellar Mass | 0.8400 M☉ |
| Bolometric Luminosity | 0.389 L☉ |
| Metallicity [Fe/H] | 0.190 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 11.980 · G: 11.624 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.037000 AU |
| Orbital Period | 2.799 days |
| Mean Orbital Velocity | 143.8 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 86.8000° |
| Mean Bulk Density | 1.53 g/cm³ (67.9 km/s vesc) |
| Insolation Flux | 332.5562 S⊕ (~452,609 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 489.000 LY (149.942 pc) |