Passage IV

As viewed from Earth, Jupiter’s 4 largest moons—the Galilean moons—appear to move relative to Jupiter along an east-west line. The farther from Jupiter a moon appears to be, the greater its angular separation, θ. Figure 1 shows these moons’ positions at midnight on a certain day in June 2012 as viewed from Earth (top section) and as viewed from above Jupiter’s north pole (bottom section).

Figure 2 shows θ for each moon from midnight on June 20, 2012, to midnight on June 28, 2012. For each moon, 1 wave cycle represents 1 orbit around Jupiter. (The time to complete 1 orbit is the time between any 2 consecutive peaks or any 2 consecutive troughs.)

Figure 2 adapted from Sylvain Rondi. Jupiter Version 2: Programme gratuit de calcul d'éphémérides des satellites galiléens de Jupiter ©2009 by Sylvain Rondi.