WASP-107 b enters the Codex as a famously fluffy warm Neptune, a low-density giant that transits a quiet K-type star about 211 light-years away. Its radius stretches to roughly 10.5 × Earth while its mass stays near Neptune’s, a Saturn-scale balloon around a heavy core. JWST spectra caught photochemical sulfur dioxide, silicate clouds, water, and a severely depleted methane inventory that points to a hot, vigorously mixed interior. Far too warm for habitability, it still rewrote cool-planet chemistry: this puffy world shows how tidal heat and starlight remake an atmosphere molecule by molecule.
