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Observations of CO and OI in Stars in Globular Clusters
Published online by Cambridge University Press: 14 August 2015
Extract
During the past decade it has been evident that the morphologies of globular cluster color-magnitude diagrams cannot be described by only two parameters, age and metal abundance (Sandage and Wildey 1967, Hartwick 1968). The third parameter is unlikely to be helium because a normal helium abundance is needed to explain the pulsation of RR Lyrae stars (Deupree 1977) and because the helium abundance of the planetary nebula in the metal-poor cluster M15 is normal (O'Dell et al. 1964).
- Type
- Part IV: HR Diagrams, Clusters
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- Copyright © Reidel 1978