TOI-172 is a Sun-like G-type star (about 1.13 solar masses, 5,645 K, 1.78 solar radii), 343 light-years from Earth. TOI-172 b is a 5.42-Jupiter-mass companion, with an orbital period of 9.5 days, at 0.091 AU from its star, and an equilibrium temperature near 1,198 K, on an eccentric orbit (e ≈ 0.38), discovered in 2019 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.