WASP-178 b

Astrophysical Synthesis & Habitability Characterization

WASP-178 b is a confirmed gas giant exoplanet orbiting the star WASP-178, located approximately 1394.9 light-years (427.68 parsecs) from the Solar System. First announced in 2019 by WASP-South using the Transit detection technique (producing an estimated primary transit depth of 1.2405% across the stellar disk), this world measures 20.288 Earth radii (1.81 Jupiter radii) and has a measured mass of 527.598 Earth masses (1.66 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.35 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.28 g⊕ (12.55 m/s²), and an escape velocity of 57 km/s.

In its orbital architecture around WASP-178, WASP-178 b completes one full revolution every 3.345 Earth days at a semi-major axis of 0.0558 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 181.5 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 2470 K (+2197°C / +3987°F) and receiving 5,550.00 S⊕ (~7,553,550 W/m²), WASP-178 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star WASP-178 is classified as a luminous A-type star of spectral type A1 IV-V with an effective photospheric temperature of 9,360 K, a radius of 1.67 R☉, a mass of 2.07 M☉, an estimated bolometric luminosity of 19.206 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.43 Gyr and a metallicity of [Fe/H] = 0.21 dex (metal-rich relative to the Sun). From Earth, WASP-178 shines at apparent V-band magnitude 9.946 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere.

Discovery Facility: WASP-South · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).