A "Hubble atlas" of ancient galaxies
Hubble Space Telescope's high resolution allows astronomers to classify galaxies in a cluster (CL 0939+4713) that existed four billion years ago, when the universe was two-thirds of its present age.
The galaxies in this mosaic are arranged according to the well-established system developed by American astronomer Edwin Hubble in the 1920s. Despite the cluster's great distance of four billion light-years, the Space Telescope pictures are sharp enough to distinguish between various forms galaxies.
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