Elliptical galaxies show very little or no internal structure and they are simply characterized by their apparent ellipticity. In general, ellipticals with major and minor axes, a and b, respectively, are typed En where n = 10 (a - b) / a. Thus E0 galaxies are apparently circular, E7 galaxies are the most flattened. When n exceeds 7, other structures appear (such as a cusp in the light distribution or rings of apparent obscuration), and the galaxy is designated as lenticular or of the S0 class.

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