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Nucleocosmochronology, or nuclear cosmochronology, is a technique used to determine timescales for astrophysical objects and events based on observed ratios of radioactive heavy elements and their decay products.
To calculate the age of formation of astronomical objects, the observed ratios of abundances of heavy radioactive and stable nuclides are compared to the primordial ratios predicted by nucleosynthesis theory.[1] Both radioactive elements and their decay products matter, and some important elements include the long-lived radioactive nuclei Th-232, U-235, and U-238, all formed by the r-process.[2] The process has been compared to radiocarbon dating.[2][3] The age of the objects are determined by placing constraints on the duration of nucleosynthesis in the galaxy.[2]
Nucleocosmochronology has been employed to determine the age of the Sun (4.57±0.02 billion years) and of the Galactic thin disk (8.8±1.8 billion years),[4][5][6] among other objects. It has also been used to estimate the age of the Milky Way itself by studying Cayrel's Star in the Galactic halo, which due to its low metallicity, is believed to have formed early in the history of the Galaxy.[7]
Limiting factors in its precision are the quality of observations of faint stars and the uncertainty of the primordial abundances of r-process elements.[citation needed]
- ^ Bland-Hawthorn, Joss; Freeman, Kenneth (2014). "Near Field Cosmology: The Origin of the Galaxy and the Local Group". The Origin of the Galaxy and Local Group. Saas-Fee Advanced Course. Vol. 37. Berlin, Heidelberg: Springer Berlin Heidelberg. pp. 1–144. Bibcode:2014SAAS...37....1B. doi:10.1007/978-3-642-41720-7_1. ISBN 978-3-642-41719-1. ISSN 1861-7980.
- ^ a b c Meyer, Bradley S; Truran, James W (2000-08-01). "Nucleocosmochronology". Physics Reports. 333–334: 1–11. Bibcode:2000PhR...333....1M. doi:10.1016/S0370-1573(00)00012-0. ISSN 0370-1573.
- ^ Symbalisty, E M D; Schramm, D N (1981-03-01). "Nucleocosmochronology". Reports on Progress in Physics. 44 (3): 293–328. doi:10.1088/0034-4885/44/3/002. ISSN 0034-4885.
- ^ del Peloso, E. F.; da Silva, L.; de Mello, G. F. Porto (April 2005). "The age of the Galactic thin disk from Th/Eu nucleocosmochronology I. Determination of [Th/Eu] abundance ratios". Astronomy & Astrophysics. 434 (1): 275–300. arXiv:astro-ph/0411698. Bibcode:2005A&A...434..275D. doi:10.1051/0004-6361:20047060. ISSN 0004-6361.
- ^ del Peloso, E. F.; da Silva, L.; Arany-Prado, L. I. (April 2004). "The age of the Galactic thin disk from Th/Eu nucleocosmochronology II. Chronological analysis". Astronomy & Astrophysics. 434 (1): 301–308. arXiv:astro-ph/0411699. doi:10.1051/0004-6361:20042438. ISSN 0004-6361.
- ^ del Peloso, E. F.; da Silva, L.; de Mello, G. F. Porto; Arany-Prado, L. I. (September 2005). "The age of the Galactic thin disk from Th/Eu nucleocosmochronology III. Extended sample". Astronomy & Astrophysics. 440 (3): 1153–1159. arXiv:astro-ph/0506458. Bibcode:2005A&A...440.1153D. doi:10.1051/0004-6361:20053307. ISSN 0004-6361.
- ^ Hill, V.; Plez, B.; Cayrel, R.; Beers, T. C.; Nordström, B.; Andersen, J.; Spite, M.; Spite, F.; Barbuy, B.; Bonifacio, P.; Depagne, E.; François, P.; Primas, F. (2002). "First stars. I. The extreme r-element rich, iron-poor halo giant CS 31082-001". Astronomy & Astrophysics. 387 (2): 560–579. arXiv:astro-ph/0203462. Bibcode:2002A&A...387..560H. doi:10.1051/0004-6361:20020434. ISSN 0004-6361. S2CID 3064681.