Some results obtained from the study of horizontal-branch (HB) morphology in a sample of galactic globular clusters are schematically presented. Scientific motivations and methodology are discussed briefly. A working scenario has been defined through the study and comparison of the HB's of M 15, M 92, NGC 5466, NGC 6752 and NGC 288. The basic conclusions drawn are: 1. The HB morphology observed in a cluster is the result of superimposed effects due to a combination, with weights that are often different from cluster to cluster, of many parameters whose individual effects may be strongly amplified in the global combination; 2. Different parameters might affect the red or the blue HB predominantly within the same cluster (for example as may be possible in M 15); 3. Stellar core rotation and structural and dynamical properties of the whole cluster may have a strong influence on the HB morphology.
Spectroscopic and Photometric Classification of Population II Stars
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