Publication Date:
2015-11-13
Description:
The first stars are predicted to have formed within 200 million years after the Big Bang, initiating the cosmic dawn. A true first star has not yet been discovered, although stars with tiny amounts of elements heavier than helium ('metals') have been found in the outer regions ('halo') of the Milky Way. The first stars and their immediate successors should, however, preferentially be found today in the central regions ('bulges') of galaxies, because they formed in the largest over-densities that grew gravitationally with time. The Milky Way bulge underwent a rapid chemical enrichment during the first 1-2 billion years, leading to a dearth of early, metal-poor stars. Here we report observations of extremely metal-poor stars in the Milky Way bulge, including one star with an iron abundance about 10,000 times lower than the solar value without noticeable carbon enhancement. We confirm that most of the metal-poor bulge stars are on tight orbits around the Galactic Centre, rather than being halo stars passing through the bulge, as expected for stars formed at redshifts greater than 15. Their chemical compositions are in general similar to typical halo stars of the same metallicity although intriguing differences exist, including lower abundances of carbon.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Howes, L M -- Casey, A R -- Asplund, M -- Keller, S C -- Yong, D -- Nataf, D M -- Poleski, R -- Lind, K -- Kobayashi, C -- Owen, C I -- Ness, M -- Bessell, M S -- Da Costa, G S -- Schmidt, B P -- Tisserand, P -- Udalski, A -- Szymanski, M K -- Soszynski, I -- Pietrzynski, G -- Ulaczyk, K -- Wyrzykowski, L -- Pietrukowicz, P -- Skowron, J -- Kozlowski, S -- Mroz, P -- England -- Nature. 2015 Nov 26;527(7579):484-7. doi: 10.1038/nature15747. Epub 2015 Nov 11.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Research School of Astronomy and Astrophysics, Australian National University, Australian Capital Territory 2601, Australia. ; Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK. ; Warsaw University Observatory, Aleje Ujazdowskie 4, 00-478 Warszawa, Poland. ; Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, Ohio 43210, USA. ; Department of Physics and Astronomy, Division of Astronomy and Space Physics, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden. ; School of Physics, Astronomy and Mathematics, Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK. ; Max-Planck-Institut fur Astronomie, Konigstuhl 17, D-69117 Heidelberg, Germany. ; Sorbonne Universites, UPMC Universite Paris 6 et CNRS, UMR 7095, Institut d'Astrophysique de Paris, 98 bis Boulevard Arago, 75014 Paris, France. ; Universidad de Concepcion, Departamento de Astronomia, Casilla 160-C, Concepcion, Chile. ; Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26560034" target="_blank"〉PubMed〈/a〉
Print ISSN:
0028-0836
Electronic ISSN:
1476-4687
Topics:
Biology
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Chemistry and Pharmacology
,
Medicine
,
Natural Sciences in General
,
Physics
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