The Classification of Galaxies: Early History and Ongoing Developments

“You ask what is the use of classification, arrangement, systematization. I answer you; order and simplification are the first steps toward the mastery of a subject—the actual enemy is the unknown.”

Settembrini to Hans Castorp in

The Magic Mountain: Thomas Mann

Discussion is made on the philosophy of classification, urging that the classification be made on the basis of morphology alone, not on the basis of supposed physics that some wish to be introduced to “explain” the classification. A history of the development of the present morphological galaxy classification system is given, starting with the purely descriptive systems of Herschel, Wolf, Shapley, and Vorontsov-Velyaminov that have no connective continuity between the classification descriptions. The development of the modern system that has an underlying continuity between the classification bins is reviewed, mainly featuring the 1926 system of Hubble that is the basis of the present extended Hubble system.