Collage of Jupiter's Moons Jupiter with the Galilean satellites in collage from Voyager 1, 1979mar: the satellites arn't to scale--they'd mostly look much smaller---but their order is correct: inner to outer Io, Europa, Ganymede, Callisto.

Galileo named the moons the Medicean satellites in honor of his patron the Medici Duke of Tuscuny, but history has named the Galilean satellites.

Credit: NASA.