The Age of the Oldest Globular Clusters

  title={The Age of the Oldest Globular Clusters},
  author={Maurizio Salaris and S. Degl'innocenti and Achim Weiss},
  journal={The Astrophysical Journal},
The age of three of the oldest clusters—M15, M68, M92—has been redetermined. We use the latest equation of state (EOS) and opacity data available for calculating both isochrones and zero-age horizontal branches and employ the brightness difference between turnoff and horizontal branch to determine the cluster age. Our procedure and the uncertainties in obtaining absolute ages are discussed in detail. We find M68 to be 12.2 ± 1.8 Gyr old; M15 appears to be either slightly younger or 2 Gyr older… 

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