Globular Cluster Ages Revisited: The Case of Ruprecht 106

Further strong evidence is presented that the Galactic globular cluster Ruprecht 106 is 'metal-poor and young', implying a delayed (about 4-5 Gyr) cluster formation within the Galactic Halo, unless it was captured from the Magellanic Clouds or other Galactic satellites. Moreover, alpha-enhanced evolutionary stellar models are necessary to explain several observed features in the color-magnitude diagram (CMD) of Ruprecht 106, in particular its red horizontal branch. Such models are necessary to yield a global self-consistency between the CMD observables and the determinations of metallicity, and age. If confirmed, this result may imply that the ages of Galactic globular clusters determined using models where only O-enhancement is taken into account should be regarded with caution.