Science: Great Cloud

The Milky Way, that river of vague light which flows across the night sky, is actually a disk-shaped galaxy of stars containing probably a hundred billion members, most of them bigger than the sun. Latest estimates of the Milky Way's diameter are about 100,000 light-years (one light-year is about six trillion miles). But there are bigger astronomical aggregations than galaxies. There are groups of galaxies which Harvard's Harlow Shapley, systematizer of the universe, calls super-galaxies or "super-systems" (TIME. July 29). Clusters bigger than super-galaxies he calls metagalactic clouds (metagalaxy is his name for...

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