SWEEPS-4 is a Sun-like G-type star (about 1.24 solar masses, 5,778 K, 1.18 solar radii). SWEEPS-4 b is a 3.80-Jupiter-mass companion, with an orbital period of 4.2 days, at 0.055 AU from its star, discovered in 2006 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. SWEEPS-4 b orbits well inside Earth's distance from the Sun. The planet's large radius (9.1 Earth radii) indicates a bloated atmosphere heated by intense stellar radiation.