Stephan's Quintet is a visual grouping of five galaxies of which four form the first compact galaxy group ever discovered. The group, visible in the constellation Pegasus, was discovered by Édouard Stephan in 1877 at the Marseille Observatory. The brightest member of the visual grouping is the spiral galaxy NGC 7320 that is shown to have extensive H II regions, identified as red blobs, where active star formation is occurring. Stephan's Quintet is the most studied of all the compact galaxy groups.Image: NASA, ESA, and the Hubble SM4 ERO team.