WASP-99 is a Sun-like F-type star (about 1.21 solar masses, 6,150 K, 1.64 solar radii), 159 light-years from Earth. WASP-99 b is a 2.43-Jupiter-mass companion, with an orbital period of 5.8 days, discovered in 2014 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 (11.4 Earth radii) indicates a bloated atmosphere heated by intense stellar radiation.