GJ 3470 b joins the Codex as a warm Neptune racing around a nearby M-type red dwarf about 96 light-years away in the constellation Cancer. Roughly 4.6 × Earth across and nearly fourteen Earth masses, it completes an orbit every 3.3 days, baking near 600 K. Hubble caught hydrogen streaming off its upper atmosphere into a vast escaping cloud, a live look at how close-in Neptunes can be whittled down toward bare cores. JWST later read water, methane, carbon dioxide, and sulfur dioxide in its metal-rich skies, with the SO₂ forged by starlight-driven photochemistry in a surprisingly cool atmosphere. It stands in the Galactic Codex as the evaporating ice giant that links the Neptune desert to modern atmospheric chemistry.
