Galilean Moons

The Galilean moons are the four largest moons of Jupiter. They receive their name from the conventional belief that they were first discovered by Galileo Galilei. However, this has recently been disputed, with some historians arguing that a number of earlier figures had sited these four moons previous to Galileo.

In order from the closest to Jupiter to the farthest away, The Galilean moons are: Io, Europa, Ganymede, and Callisto.

At their closest distance to Earth, Ganymede has a magnitude of 4.6 and Callisto one of 5.6. At its apsis, Io is separated from Jupiter by roughtly two arc minutes. It is theoretically possible that the most dedicated and well-trained observers could see the moons from Earth with the naked eye, but it has not yet been authoritatively proven that anyone has ever done this sucessfully.