... Callisto's surface shows its age. ... Io's surface is young, shows practically no impact craters, and is continually being repaved by the lava exploding from its many large volcanoes . Stars Without Galaxies . ... Galaxies are made up of stars, but are all stars found within galaxies? ... Pick a Galaxy Any Galaxy . ... Typical of large galaxy clusters billions of light-years away, Abell 2597 features hundreds of galaxies embedded in a cloud of multimillion degree gas which glows in x-rays. ...