{"schema":"pubphys.bundle/1","record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"442decd16c70258f99cb6da928901a87579da4d79467b97dbe555fc841f8df7a","created":"2026-10-03T07:18:02Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"7683fa5b140e8f64f23cdd4cb4dbe1c4e34c749c8b0509fda1f0fd964c63d716","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"yes-no","assisted_by":[],"external_id":"cosmo.cosmic-dawn.population-iii-stars","kind":"well-posed","literature_status":"open","n":"1","parents":[],"plain":"The very first stars formed from pure hydrogen and helium and are predicted to have been very massive and short-lived. No such star system has been confirmed, though JWST has found candidates.","posed_since":"","precise":"Identify a stellar system with gas metallicity below the critical value $Z_{\\mathrm{crit}}$ (theoretical range about $1e-6\\ \\text{to}\\ 1e-3.5\\ Z_{\\mathrm{sun}}$), strong $\\mathrm{He}\\ \\mathrm{II}\\ 1640\\ \\text{Angstrom}$ emission and no detected metal lines, consistent with a top-heavy initial mass function. The leading candidate is LAP1 at $z \\sim 6.6$, lensed by the cluster MACS J0416. An answer is a confirmed detection with metal-line upper limits below $Z_{\\mathrm{crit}}$, or a measured upper bound on the Population III star-formation rate density at $z > 6$.","problem_ref":null,"references":"","settled_by":"Deep JWST spectroscopy of lensed candidates reaching metal-line limits below $Z_{\\mathrm{crit}}$ together with He II equivalent widths.","status_note":"Visbal, Hazlett and Bryan (2025, arXiv:2508.03842) argue that LAP1-B matches three theoretical Population III predictions; confirmation is pending.","title":"Have metal-free Population III stars been 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