The Coma Cluster
The extensively studied Coma cluster, lying near the north galactic pole and nearly 100 megaparsecs away, contains more than 1000 bright galaxies. A note of interest about this image: it shows the merging of the larger, brighter central cluster and the fainter group of galaxies to the lower right. The field of the image is 2.7 degrees wide by 2.5 degrees high.
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(Image courtesy of U. Briel, MPE Garching, Germany and ESA.)