HAT-P-40 is a Sun-like F-type star (about 1.03 solar masses, 6,080 K, 1.94 solar radii), 464 light-years from Earth. HAT-P-40 b is a 0.48-Jupiter-mass companion, with an orbital period of 4.5 days, 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 (17.0 Earth radii) indicates a bloated atmosphere heated by intense stellar radiation.