This Hubble Space Telescope image shows Messier 15, an ancient star cluster in Pegasus. It contains some of the oldest stars in the galaxy. Some of its stars are nearing the ends of their lives so they're puffing up and getting cooler, shining dull orange. One star has already passed this stage of life, sloughing off its outer layers to form a planetary nebula (blue blob to the lower left of center). [ESA-Hubble/NASA]