Concentration Classes of Globular Clusters

as illustrated by the Messier Globular Clusters

The classification scheme most widely used for globular clusters was developed by Harlow Shapley and Helen B. Sawyer Hogg in the 1920s (Shapley 1930). They introduced Concentration Classes, sometimes referred to as Shapley-Sawyer Concentration Classes, which are named by numbers and typically denoted as Roman numbers, from I-XII, or 1-12, where I (1) denotes the highest concentration or most concentrated, densest structure, and XII the least concentrated.

Below please find this classification scheme illustrated with images of the Messier's Globular Clustersr.

If your browser doesn't support tables, try this version.

Class I      

Class II     
                M2      M80

Class III    

Class IV     
                M15     M28     M62     M92

Class V      
               M5     M13       M30       M53     M69    M70     M79

Class VI     

Class VII    
                M10      M22

Class VIII   
                M9      M14      M19

Class IX     
                M4     M12      M72

Class X      
                M56      M68      M107

Class X-XI   

Class XI     

Class XII    -


Hartmut Frommert

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Last Modification: February 19, 2014