Have metal-free Population III stars been observed?
In plain words
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.
Precise statement
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 $z > 6$.
What would settle it
Deep JWST spectroscopy of lensed candidates reaching metal-line limits below $Z_{\mathrm{crit}}$ together with He II equivalent widths.
Status in the literature
Unverified note
Visbal, Hazlett and Bryan (2025, arXiv:2508.03842) argue that LAP1-B matches three theoretical Population III predictions; confirmation is pending.