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Enrichment by the first stars in a relic dwarf galaxy

Chiti, Anirudh ; Placco, Vinicius M. ; Pace, Andrew B. ; Ji, Alexander P. ; Prabhu, Deepthi S. ; Cerny, William ; Limberg, Guilherme ; Stringfellow, Guy S. ; Drlica-Wagner, Alex and Atzberger, Kaia R. , et al. (2026) In Nature Astronomy
Abstract

Stars that contain trace amounts of elements heavier than helium (that is, ‘metallicity’) preserve the chemical fingerprints of the first stars. In the Milky Way, nearly all of the lowest-metallicity stars show an extreme over-abundance of carbon. The origin of this signature has remained a mystery owing to the lack of observational constraints on the environments in which it originates. Here we present observations of a star in the >10-billion-year-old ultrafaint dwarf galaxy Pictor II, showing the lowest iron and calcium abundances outside the Milky Way (<1/43,000th solar and ~1/160,000th solar), with >3,000× relative carbon enhancement. The star’s exceptional paucity in iron and calcium make it clearly preserve enrichment... (More)

Stars that contain trace amounts of elements heavier than helium (that is, ‘metallicity’) preserve the chemical fingerprints of the first stars. In the Milky Way, nearly all of the lowest-metallicity stars show an extreme over-abundance of carbon. The origin of this signature has remained a mystery owing to the lack of observational constraints on the environments in which it originates. Here we present observations of a star in the >10-billion-year-old ultrafaint dwarf galaxy Pictor II, showing the lowest iron and calcium abundances outside the Milky Way (<1/43,000th solar and ~1/160,000th solar), with >3,000× relative carbon enhancement. The star’s exceptional paucity in iron and calcium make it clearly preserve enrichment from the first stars in a relic dwarf galaxy; Pictor II is one of the smallest, most chemically primordial systems known. This star supports the hypothesis that extreme carbon enhancement results from low-energy supernovae from the first stars, as the yields of energetic supernovae are harder to retain in small-scale environments. This signature of enrichment by the first stars may trace a regime inaccessible to current high-redshift observations, which can hardly detect the initial enrichment of the smallest galaxies.

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in press
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Nature Astronomy
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Nature Publishing Group
external identifiers
  • scopus:105033822661
ISSN
2397-3366
DOI
10.1038/s41550-026-02802-z
language
English
LU publication?
yes
additional info
Publisher Copyright: © The Author(s), under exclusive licence to Springer Nature Limited 2026.
id
10d7530d-47c1-4b8b-994a-ef88d0e94169
date added to LUP
2026-05-20 15:39:11
date last changed
2026-05-21 10:17:26
@article{10d7530d-47c1-4b8b-994a-ef88d0e94169,
  abstract     = {{<p>Stars that contain trace amounts of elements heavier than helium (that is, ‘metallicity’) preserve the chemical fingerprints of the first stars. In the Milky Way, nearly all of the lowest-metallicity stars show an extreme over-abundance of carbon. The origin of this signature has remained a mystery owing to the lack of observational constraints on the environments in which it originates. Here we present observations of a star in the &gt;10-billion-year-old ultrafaint dwarf galaxy Pictor II, showing the lowest iron and calcium abundances outside the Milky Way (&lt;1/43,000th solar and ~1/160,000th solar), with &gt;3,000× relative carbon enhancement. The star’s exceptional paucity in iron and calcium make it clearly preserve enrichment from the first stars in a relic dwarf galaxy; Pictor II is one of the smallest, most chemically primordial systems known. This star supports the hypothesis that extreme carbon enhancement results from low-energy supernovae from the first stars, as the yields of energetic supernovae are harder to retain in small-scale environments. This signature of enrichment by the first stars may trace a regime inaccessible to current high-redshift observations, which can hardly detect the initial enrichment of the smallest galaxies.</p>}},
  author       = {{Chiti, Anirudh and Placco, Vinicius M. and Pace, Andrew B. and Ji, Alexander P. and Prabhu, Deepthi S. and Cerny, William and Limberg, Guilherme and Stringfellow, Guy S. and Drlica-Wagner, Alex and Atzberger, Kaia R. and Choi, Yumi and Crnojević, Denija and Ferguson, Peter S. and Kallivayalil, Nitya and Noël, Noelia E.D. and Riley, Alexander H. and Sand, David J. and Simon, Joshua D. and Walker, Alistair R. and Bom, Clecio R. and Carballo-Bello, Julio A. and James, David J. and Martínez-Vázquez, Clara E. and Medina, Gustavo E. and Vivas, A. Katherina}},
  issn         = {{2397-3366}},
  language     = {{eng}},
  publisher    = {{Nature Publishing Group}},
  series       = {{Nature Astronomy}},
  title        = {{Enrichment by the first stars in a relic dwarf galaxy}},
  url          = {{http://dx.doi.org/10.1038/s41550-026-02802-z}},
  doi          = {{10.1038/s41550-026-02802-z}},
  year         = {{2026}},
}