D100 spiral galaxy with a tail of gas (red). The galaxy is a member of the Coma galaxy cluster. D100's tail of gas, which stretches far beyond the left of this image, is caused by hot plasma in the cluster stripping gas from the galaxy as it moves through space. A phenomenon known as ram-pressure stripping. Densely populated clusters such as Coma, are home to thousands of galaxies and are used to study ram-pressure stripping, which can have a profound effect on how galaxies evolve and form new generations of stars. This image combines data from the NASA/ESA Hubble Space Telescope Advanced Camera for Surveys and the Subaru Telescope in Hawaii.