WASP-54 is a Sun-like F-type star (about 1.08 solar masses, 6,100 K, 1.76 solar radii), 251 light-years from Earth. WASP-54 b is a 0.59-Jupiter-mass companion, with an orbital period of 3.7 days, on an eccentric orbit (e ≈ 0.07), discovered in 2012 via transit. The inner world is a hot Jupiter — a gas giant hugging its star at a fraction of Mercury's distance — a class that forced astronomers to rethink how giant planets form and migrate inward. The planet's large radius (17.7 Earth radii) indicates a bloated atmosphere heated by intense stellar radiation.