Jupiter and its Galilean moons Montage of images of Jupiter and its four largest satellites These are known as the Galilean moons as they were discovered by the astronomer Galileo in The moons in order of increasing orbital distance from Jupiter are Io second right Europa centre Ganymede right and Callisto foreground The Galileans are by far the largest moons in the Jupiter system ranging from km to km diameter The other moons of Jupiter range between and km across The images of Jupiter and the Galilean moons used in this montage were gathered by Voyager spacecraft in