TRAPPIST-1 b opens the Codex ledger for the innermost world of the seven-planet TRAPPIST-1 system, an ultracool M-dwarf neighborhood already partly mapped here. About 1.1 × Earth across and 41 light-years away, it races around its red dwarf every 1.5 days, locked with one face forever sunward. JWST’s mid-infrared gaze measured a scorching dayside near 500 K, a thermal signature that matches bare rock far better than a thick, heat-sharing atmosphere. Too close for the habitable zone, it still matters: this scorched sibling teaches how rocky worlds weather the fierce light of tiny stars, and it anchors the TRAPPIST sequence the Codex keeps returning to.
