HAT-P-3 is an orange K-type dwarf (about 1.06 solar masses, 5,185 K, 0.87 solar radii), 135 light-years from Earth. HAT-P-3 b is a 0.65-Jupiter-mass companion, with an orbital period of 2.9 days, discovered in 2007 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 (10.5 Earth radii) indicates a bloated atmosphere heated by intense stellar radiation.