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.

26. Thebe is one of Jupiter’s smaller moons. Thebe completes 1 orbit of Jupiter in approximately 0.7 days. Based on Figure 2, regardless of direction, the maximum value of θ for Thebe is most likely:

Answer and Explanation

Your Answer is

Correct Answer is F

Explanation

Combined with figures 1 & 2, it can be found that the closer the satellite is to Jupiter, the shorter the period of operation, and the smaller the extreme value of θ. The period of the satellite Thebe mentioned in the title is shorter than that of Io, indicating that the maximum value of θ will be smaller than that of Io, which is about 7 or less.