“There exists also another type of galaxy agglomeration. These have diameters between roughly one and ten times those of large clusters, but have much smaller densitities; they are usually irregular, with patchy density variations and no central concentration. The larger and most conspicuous of these agglomerations may contain several clusters, which explains why they have been given the name "superclusters." In their longer dimensions, crossing times exceed the age of the Universe. They are thus unrelaxed. Unrelaxed apperance, together with large size, might be taken as a definition of superclusters.”

—  Jan Oort

(quote from p. 373)

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Jan Oort 5
Dutch astronomer 1900–1992

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