Kepler-15 is a Sun-like G-type star (about 1.02 solar masses, 5,515 K, 0.99 solar radii), 739 light-years from Earth. Kepler-15 b is a 0.66-Jupiter-mass companion, with an orbital period of 4.9 days, at 0.057 AU from its star, on an eccentric orbit (e ≈ 0.06), discovered in 2011 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.