University of Michigan - Department of Astronomy

Version: Age Worksheet

Galactic Star Clusters Cluster Age Worksheets


Table 1: Cluster Data

Cluster Name (B-V)o
at Turn-Off
Cluster Age
M 67    
M 45    
M 44    
M 25    
NGC 752    
NGC 6791    
NGC 7044    
Mel 20    


  1. Draw a sketch of a color-magnitude diagram, and indicate which regions in the chart represent red/blue, bright/dim, and cool/hot stars. What kind of stars live in each region?

  2. Cluster Mel 20 contains objects in the lower right of the CMD that are not on the main sequence. These are not evolved red giant stars -- how can you tell? What stage of stellar evolution do they represent?

  3. While there was quite a bit of variation in the clusters we looked at, none of them was as old as a globular cluster (these were galactic clusters). If you were to look at a color-magnitude diagram of a very, very old cluster, what would you expect to see? Draw a sketch as well as explain any new features.

  4. Could you use the technique we have used here to find the age of a single star (not in a cluster)? Why/why not? In general, can you tell anything about the age of a single star from an H-R diagram?

Last Update: 8/30/07 by SAM

original LA&GB

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