The First Stars

The formation of the first luminous objects in the universe

The first generation of stars formed a few hundred million years after the Big Bang out of nearly pure hydrogen and helium gas. Early simulations showed that these Population III stars were likely massive and short-lived, and that their radiation, supernovae, and metals set the initial conditions for all subsequent galaxy formation (Abel et al., 2002).

Our recent work follows this story forward with the AEOS project: star-by-star cosmological simulations that track individual stars, their feedback, and the dispersal of their nucleosynthetic products through the first galaxies (Brauer et al., 2025). These calculations show how unevenly the first metals are mixed into the early interstellar and intergalactic medium (Mead et al., 2025; Mead et al., 2026), how the assumed Population III initial mass function shapes early chemical enrichment (Brauer et al., 2025), and how to extend these results to larger volumes with calibrated semi-analytic models (Hazlett et al., 2025).

This field is now becoming observational: lensed systems at high redshift are reaching the sensitivity needed to test these predictions directly (Visbal et al., 2025), and the chemical fingerprints of the first stars may also be recoverable from damped Lyman-α absorbers near the epoch of reionization (Visbal et al., 2026).

References

2026

  1. ApJ
    AEOS Is Mixing It Up: The (In)homogeneity of Metal Mixing Following Population III Star Formation
    Jennifer Mead, Kaley Brauer, Greg L. Bryan, and 7 more authors
    The Astrophysical Journal, May 2026
    DOI HTML
  2. JCAP
    Chemical signatures of Population III stars in damped Lyman-α absorption systems at z ≍ 6
    Eli Visbal, Greg L. Bryan, and Zoltán Haiman
    Journal of Cosmology and Astroparticle Physics, Feb 2026
    DOI arXiv HTML

2025

  1. ApJ
    AEOS: Star-by-star Cosmological Simulations of Early Chemical Enrichment and Galaxy Formation
    Kaley Brauer, Andrew Emerick, Jennifer Mead, and 7 more authors
    The Astrophysical Journal, Feb 2025
    DOI arXiv HTML
  2. ApJ
    AEOS: Transport of Metals from Minihalos following Population III Stellar Feedback
    Jennifer Mead, Kaley Brauer, Greg L. Bryan, and 7 more authors
    The Astrophysical Journal, Feb 2025
    DOI arXiv HTML
  3. ApJ
    AEOS: The Impact of Population III Initial Mass Function and Star-by-star Models in Galaxy Simulations
    Kaley Brauer, Jennifer Mead, John H. Wise, and 7 more authors
    The Astrophysical Journal, Nov 2025
    DOI arXiv HTML
  4. arXiv
    From Primordial Stars to Early Galaxies: A Semi-Analytic Model Calibrated with Aeos and Renaissance
    Ryan Hazlett, Jennifer Mead, Eli Visbal, and 6 more authors
    arXiv e-prints, Oct 2025
    DOI arXiv HTML
  5. ApJ
    LAP1-B is the First Observed System Consistent with Theoretical Predictions for Population III Stars
    Eli Visbal, Ryan Hazlett, and Greg L. Bryan
    The Astrophysical Journal, Nov 2025
    DOI arXiv HTML

2002

  1. Science
    The Formation of the First Star in the Universe
    Tom Abel, Greg L. Bryan, and Michael L. Norman
    Science, Jan 2002
    DOI arXiv HTML