Abstract
THE age of the Galaxy may be estimated from observations of the ratio of stellar abundances of thorium, which has only one long-lived isotope with a half-life comparable to the suspected age of the Galaxy, and neodymium, a stable element. The Th/Nd abundance ratio in a sample of G-dwarf stars of different ages was derived by Butcher1 from the intensities of one Th II and one Nd II absorption line, and indicated a rather young galactic age of 9.6 Gyr. But the Th II line is blended with a Co I line. Here we determine the transition probability of the Co I line by combining radiative lifetime and branching-ratio measurements. We show that the Co I contribution cannot be neglected in deriving Th/Nd ratios. By comparing our results with predictions based on models of galactic chemical evolution, we suggest a revised age of the Galaxy of 15–20 Gyr.
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References
Butcher, H. R. Nature 328, 127–131 (1987).
Holweger, H. Observatory 100, 155–160 (1980).
Duquette, D. W. & Lawler, J. E. Phys. Rev. A26, 330–334 (1982).
Brault, J. W. J. opt. Soc. Am. 66, 1081 (1976).
Adams, D. L. & Whaling, W. J. opt. Soc. Am. 71, 1036–1038 (1981).
Lawler, J. E. Springer Ser. opt. Sci. 54, 125–140 (1988).
Anders, E. & Grevesse, N. Geochim. cosmochim. Acta 53, 197–214 (1989).
Holweger, H. & Muller, E. A. Solar Phys. 39, 19–30 (1974).
Delbouille, L., Neven, L. & Roland, G. Photometric Atlas of the Solar Spectrum from 3000 to 10000 Ā (Institut d'Astrophysique, Université de Liege, 1973).
Simonsen, H., Worm, T., Jessen, P. & Poulsen, O. Physica Scripta 38, 370–373 (1988).
Palmer, B. A. & Engleman, R. Jr Atlas of the Thorium Spectrum, LA-9615 (Los Alamos National Laboratory, 1983).
Irwin, A. W. Astrophys. J., Suppl. Ser. 45, 621–633 (1981).
Corliss, C. H. & Bozman, W. R. Natn. Bur. Stand. Monogr. 53 (1962).
Kurucz, R. L. Astrophys. J., Suppl. Ser. 40, 1–340 (1979).
Peytremann, E. Astr. Astrophys., Suppl. Ser. 18, 81–133 (1974).
Ward, L., Vogel, O., Arnesen, A., Hallin, P. & Wannstrom, A. Physica Scripta 31, 161–165 (1985).
Arnould, M. & Takahashi, K. Proc. 5th IAP Meeting on Astrophysical Ages and Dating Methods (eds Vangioni-Flam, E., Cassé, M., Audouze, J. & Tran Thanh Van, J.) 325–348 (Editions Frontiéres, Gif-sur-Yvette, 1990).
Mathews, G. J. & Schramm, D. N. Astrophys. J. 324, L67–L70 (1988).
Butcher, H. R. Messenger 51, 12–14 (1988).
Krishnaswamy-Gilroy, K., Sneden, C., Pilachowski, C. A. & Cowan, J. J. Astrophys. J. 327, 298–320 (1988).
Butcher, H. R. Astrophys. J. 199, 710–717 (1975).
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Lawler, J., Whaling, W. & Grevesse, N. Contamination of the Th II line and the age of the Galaxy. Nature 346, 635–637 (1990). https://doi.org/10.1038/346635a0
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DOI: https://doi.org/10.1038/346635a0
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