A simplified illustration of the parallax of an object against a distant background due to a perspective shift. When viewed from Viewpoint A, the object appears to be in front of the blue square. When the viewpoint is changed to Viewpoint B, the object appears to have moved in front of the red square.
From top to bottom: Io, Europa, Ganymede, Callisto. The Galilean moons are the four largest moons of JupiterâIo, Europa, Ganymede, and Callisto. They were discovered by Galileo Galilei around January 1610 and were the first group of objects found to orbit another planet. Their names derive from the lovers of Zeus.
This gives Jupiter the largest number of moons with reasonably secure orbits of any planet in the Solar System. The most massive of them, the four Galilean moons, were discovered in 1610 by Galileo Galilei and were the first objects found to orbit a body that was neither Earth nor the Sun. Inner satellites or Amalthea group: Metis, Adrastea, Amalthea, and Thebe. 2  These orbit very close to Jupiter; the innermost two orbit in less than a Jovian day. 3  The latter two are respectively the fifth and seventh largest moons in the Jovian system.