|Annu. Rev. Astron. Astrophys. 1996. 34:
Copyright © 1996 by Annual Reviews. All rights reserved
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Department of Physics and Astronomy, University of Victoria, P. O. Box 3055, Victoria, British Columbia, Canada V8W 3P6
UCO/Lick Observatory, University of California, Santa Cruz, California 95064
Dominion Astrophysical Observatory, Herzberg Institute of Astrophysics, National Research Council of Canada, 5071 West Saanich Road, Victoria, British Columbia, V8X 4M6 Canada
ABSTRACT. A careful assessment of current uncertainties in stellar physics (opacities, nuclear reaction rates, equation of state effects, diffusion, rotation, and mass loss), in the chemistry of globular cluster (GC) stars, and in the cluster distance scale, suggests that the most metal-poor (presumably the oldest) of the Galaxy's GCs have ages near 15 Gyr. Ages below 12 Gyr or above 20 Gyr appear to be highly unlikely. If these 2 limits are increased by ~ 1 Gyr to account for the formation time of the globulars, and if standard Friedmann cosmologies with the cosmological constant set to zero are assumed, then the GC constraint on the present age of the Universe (t0 13 Gyr) implies that the Hubble constant H0 51 km s-1 Mpc-1 if the density parameter = 1 or 62 km s-1 Mpc-1 if = 0.3.
Key words: globular clusters, stellar structure, stellar evolution, ages, subdwarfs, RR Lyrae stars, chemical abundances, cosmology
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1 Killam Research Fellow. Back.