Abstract The light element lithium is formed by nucleosynthesis during the Big Bang. Its abundance can help to define the parameters of the early Universe. To find this primordial value, it is necessary to determine Li abundances in the oldest stars because it is readily destroyed by nuclear reactions in stellar interiors. We have made high-resolution (∼45,000) spectroscopic observations of five identical unevolved turnoff stars in the 13 Gyr old globular cluster M5. In our analysis we find a range in Li abundance of a factor of 2; the spread is 5 times the individual error. The comparison of these results with those for turnoff stars from five other globular clusters reveals a similarly large range in Li. Lithium in M5 and the other clusters all have stars above the field star Li plateau, but none are as high as the predictions for primordial Li. The maximum values for Li are the same in all six clusters. Multiple generations of stars are found in many globular clusters; those later generations are expected to have formed from Li-depleted gas. Such second- and later-generation stars would have no Li. However, only one of the six clusters has a few unevolved stars with upper limits on the Li abundance.
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The Cosmic Lithium Story
Lithium’s story spans the history of the universe and is one that links to all its largest-scale processes: big bang nucleosyntheses, the evolution of stars, and galactic chemical evolution. Lithium was the only metal produced in the big bang, alongside the gases H and He. Stars destroy both stable isotopes of Li easily, yet we still have Li today, even after generations of stars have come and gone. Ongoing production of Li by galactic cosmic rays and by a limited number of Li-producing nuclear reactions and transport processes in some rare types of stars keeps lithium present in the universe.
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- Award ID(s):
- 1517541
- PAR ID:
- 10642795
- Publisher / Repository:
- Mineralogical Society of America and the Geochemical Society
- Date Published:
- Journal Name:
- Elements
- Volume:
- 16
- Issue:
- 4
- ISSN:
- 1811-5209
- Page Range / eLocation ID:
- 241 to 246
- Subject(s) / Keyword(s):
- lithium big bang stars brown dwarfs nucleosynthesis abundances 6Li 7Li meteorites solar system
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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