HD 189733 is an orange K-type dwarf (about 0.79 solar masses, 5,052 K, 0.75 solar radii), 19.8 light-years from Earth. HD 189733 b was the first exoplanet with a weather map, a deep-blue hot Jupiter whose day-to-night temperature contrast has been measured. HD 189733 b is a 1.13-Jupiter-mass companion, with an orbital period of 2.2 days, discovered in 2005 via radial velocity. 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 (12.7 Earth radii) indicates a bloated atmosphere heated by intense stellar radiation.