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arXiv · astro-ph/9403064

Possible Systematic Decreases in the Age of Globular Clusters

X. Shi·D. N. Schramm·D. S. P. Dearborn·J. W. Truran
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Abstract

The ages of globular clusters inferred from observations depends sensitively on assumptions like the initial helium abundance and the mass loss rate. A high helium abundance (e.g., $Y\approx$0.28) or a mass loss rate of $\sim$10$^{-11}M_\odot$ yr$^{-1}$ near the main sequence turn-off region lowers the current age estimate from 14 Gyr to about 10--12 Gyr, significantly relaxing the constraints on the Hubble constant, allowing values as high as 60km/sec/Mpc for a universe with the critical density and 90km/sec/Mpc for a baryon-only universe. Possible mechanisms for the helium enhancement in globular clusters are discussed, as are arguments for an instability strip induced mass loss near the turn-off. Ages lower than 10 Gyr are not possible even with the operation of both of these mechanisms unless the initial helium abundance in globular clusters is $>0.30$, which would conflict with indirect measurements of helium abundances in globular clusters.

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X. Shi, D. N. Schramm, D. S. P. Dearborn, J. W. Truran. 1994-03-29. Possible Systematic Decreases in the Age of Globular Clusters. https://arxiv.org/abs/astro-ph/9403064

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