What were the first stars (Population III) like?
The first stars formed from pure hydrogen–helium gas with no metals to cool it, so models predict they were massive (tens to hundreds of solar masses) and short-lived, seeding the first heavy elements and possibly the first black holes. None has been directly observed.
Why it is hard
Pop III stars lived at z > 10–20, too faint and redshifted even for JWST as individual objects. Their signatures must be extracted indirectly — from chemical abundances in ancient halo stars, 21-cm signals, or statistical light in the cosmic infrared background.
Current evidence
Hyper-metal-poor halo stars show abundance patterns consistent with enrichment by single massive Pop III supernovae; some show pair-instability-like signatures. JWST has found candidate Pop III-hosting clusters and GN-z11's unusual nitrogen abundance, but confirmation remains elusive.
Possible approaches
Stellar archaeology of ultra-metal-poor stars, 21-cm cosmology (HERA, SKA-low), JWST spectroscopy of lensed arc systems, and gravitational-wave detection of Pop III remnant black-hole mergers.
Related topics
Sources
- Webb Telescope Overview — NASA Science
- Relevant Documents for SKA Science Users — SKA Observatory
- Astronomy 2e — Evolution from the Main Sequence to Red Giants — OpenStax
- How Herschel unlocked the secrets of star formation — European Space Agency