WASP-99 b

Astrophysical Synthesis & Habitability Characterization

WASP-99 b is a confirmed gas giant exoplanet orbiting the star WASP-99, located approximately 517.5 light-years (158.66 parsecs) from the Solar System. First announced in 2014 by SuperWASP using the Transit detection technique (producing an estimated primary transit depth of 0.4085% across the stellar disk), this world measures 11.433 Earth radii (1.02 Jupiter radii) and has a measured mass of 772.327 Earth masses (2.43 Jupiter masses). Combining its mass and radius yields a mean bulk density of 2.85 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 5.91 g⊕ (57.96 m/s²), and an escape velocity of 91.9 km/s.

In its orbital architecture around WASP-99, WASP-99 b completes one full revolution every 5.753 Earth days at a semi-major axis of 0.0717 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 135.6 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 1480 K (+1207°C / +2205°F) and receiving 2,005.43 S⊕ (~2,729,385 W/m²), WASP-99 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star WASP-99 is classified as a warm F-type star of spectral type F8 with an effective photospheric temperature of 6,150 K, a radius of 1.64 R☉, a mass of 1.21 M☉, an estimated bolometric luminosity of 3.452 L☉. Stellar evolution modeling indicates an estimated stellar age of 3 Gyr and a metallicity of [Fe/H] = 0.21 dex (metal-rich relative to the Sun). From Earth, WASP-99 shines at apparent V-band magnitude 9.475 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere.

Discovery Facility: SuperWASP · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).