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.

23. Based on Figure 2, as viewed from Earth at midnight on June 27, which Galilean moon appeared farthest west of Jupiter?

Answer and Explanation

Your Answer is

Correct Answer is C

Explanation

Many people will wonder whether the midnight on June 27 refers to the beginning or the end of the 27th. Refer to the description of midnight on Wikipedia "Though there is no global unanimity on the issue, most often midnight is considered the start of a new day and is associated with the hour 00:00," we understand the time of this question as the beginning of the 27th.

Then we find the place where the abscissa in figure 2 is 27, corresponding to the ordinates of several lines, and find that Ganymede is the farthest satellite to the west of Jupiter