This dense region of galaxies is called the Coma Cluster. Only 350 million light years away, it contains about 800 galaxiesΓÇöthe richest galaxy cluster close to Earth. Of all the objects visible in this image only the blue one in the upper right is a star in the Milky Way; all others are entire galaxies. The two largest are giant elliptical galaxies, known to astronomers as cD galaxies; these galaxies, found at the center of galaxy clusters, grow to such enormous size by consuming vast amounts of intergalactic gas and even other galaxies. The giant ellipticals here appear reddish because they contain mostly older stars.
Like most rich galaxy clusters, the Coma Cluster contains few
