{
  "abstract": "We present a new determination of the primordial helium abundance based on new, high-quality Large Binocular Telescope (LBT) observations of 54 metal-poor H ii regions. These regions have been observed and analyzed uniformly. We also describe a number of updates to our methodology, including updated helium emissivities. Enabled by the large, high-quality dataset, we examine our sample targets for potential systematic errors, which could bias their results. We perform a standard 95% confidence level (CL) χ 2 cut and find that a significantly larger fraction (47/54 = 87%) of our sample qualifies than for previous datasets. We also screen for quality and reliability, flagging targets that may introduce significant systematic errors, producing a dataset of 41 targets. In a significant breakthrough for the field, that dataset includes 15 high signal-to-noise ratio (SNR) targets with low metallicity (O/H ≤ 4 × 10 −5 ). Due to this low-metallicity dataset, for the first time, a weighted average for determining the primordial helium abundance ( y p ) is well justified and produces a robust result. By weighted average of our 15 low-metallicity targets, we determine y p = 0.08146 ± 0.00058, with the corresponding mass fraction Y p = 0.2458 ± 0.0013. This result achieves an unprecedented precision of 0.5%, and it is in good agreement with the Big Bang nucleosynthesis (BBN) result, Y p = 0.2467 ± 0.0002, based on the Planck determination of the baryon density.",
  "abstract_shown": true,
  "affiliations": [
    "Gonzaga University",
    "University of Minnesota",
    "The Ohio State University",
    "Northwestern University",
    "The University of Texas at Austin",
    "Indiana University",
    "Universidad Nacional Autónoma de México"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 10,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "Erik Aver",
      "orcid": "0009-0006-2077-2552"
    },
    {
      "affs": [
        1
      ],
      "name": "Evan D. Skillman",
      "orcid": "0000-0003-0605-8732"
    },
    {
      "affs": [
        2
      ],
      "name": "Richard W. Pogge",
      "orcid": "0000-0003-1435-3053"
    },
    {
      "affs": [
        3
      ],
      "name": "Noah S. J. Rogers",
      "orcid": "0000-0002-0361-8223"
    },
    {
      "affs": [
        2
      ],
      "name": "Miqaela K Weller",
      "orcid": "0000-0003-4912-5157"
    },
    {
      "affs": [
        1
      ],
      "name": "Keith A. Olive",
      "orcid": "0000-0001-7201-5998"
    },
    {
      "affs": [
        4
      ],
      "name": "Danielle A. Berg",
      "orcid": "0000-0002-4153-053X"
    },
    {
      "affs": [
        5
      ],
      "name": "John J. Salzer",
      "orcid": "0000-0001-8483-603X"
    },
    {
      "affs": [
        1
      ],
      "name": "John H Miller",
      "orcid": "0000-0002-2901-5260"
    },
    {
      "affs": [
        6
      ],
      "name": "J. Eduardo Méndez-Delgado",
      "orcid": "0000-0002-6972-6411"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/3w35p00nyxczx.bib",
  "cited_by": 28,
  "doi": "10.3847/1538-4357/ae879b",
  "fulltext_url": null,
  "id": "3w35p00nyxczx",
  "issns": [
    "0004-637X",
    "1538-4357"
  ],
  "landing_url": "https://doi.org/10.3847/1538-4357/ae879b",
  "language": "en",
  "licence": "CC-BY",
  "licence_label": "CC BY",
  "licence_source": "journal",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "openalex",
      "3103|Stellar, planetary, and galactic studies"
    ]
  ],
  "openalex": "W7212022986",
  "pdf_url": "https://iopscience.iop.org/article/10.3847/1538-4357/ae879b/pdf",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-09",
  "publisher": "IOP Publishing",
  "ris": "https://research.draconitic.com/paper/3w35p00nyxczx.ris",
  "sources": [
    {
      "first_seen": "2026-11-04T13:21:02Z",
      "native_id": "W7212022986",
      "source": "openalex",
      "url": "https://doi.org/10.3847/1538-4357/ae879b"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "openalex:3103|Stellar, planetary, and galactic studies",
      "subfield": "stellar"
    }
  ],
  "title": "The LBT Y p Project. IV. A New Value of the Primordial Helium Abundance",
  "title_text": "The LBT Y p Project. IV. A New Value of the Primordial Helium Abundance",
  "type": "peer-reviewed",
  "updated_at": "2026-11-09T13:21:02Z",
  "url": "https://research.draconitic.com/paper/3w35p00nyxczx",
  "venue": "The Astrophysical Journal",
  "versions": []
}