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.
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Class I M75 Class II M2 M80 Class III M54 Class IV M15 M28 M62 M92 Class V M5 M13 M30 M53 M69 M70 M79 Class VI M3 Class VII M10 M22 Class VIII M9 M14 M19 Class IX M4 M12 M72 Class X M56 M68 M107 Class X-XI M71 Class XI M55 Class XII -
Last Modification: February 19, 2014