Dwarf Galaxies in the Coma Cluster . ... JPL-Caltech , SDSS , NASA Explanation: In visible light images, over a thousand galaxies are seen to lie within a volume about 20 million light-years across in the rich Coma Galaxy Cluster . ... This composite combines infrared Spitzer Space Telescope image data (red and green) with visible light Sloan Sky Survey data (blue) for the central part of the cluster. ... Dwarf galaxies are thought to form first, providing building blocks for larger galaxies. ...