Using the Web

Go to Sky & Telescope’s “Jupiter’s Moons” Web page ( Enter your date and time. Where are the four Galilean moons? Keep clicking on “+1 hour” to see how their positions change over time. Which moon passes in front of (transits) Jupiter? If possible, observe these moons for a couple of nights through a small telescope, binoculars, or telephoto camera lens. Sketch the positions of the moons.
Look at the updated lists of Jupiter’s moons on NASA’s “Our Solar System” page (; click on “Jupiter” and “Moons”) and on the Carnegie Institution of Washington Department of Terrestrial Magnetism’s (DTM) “Jupiter Satellite Page” ( What are two of the more recently discovered moons? Are the orbits retrograde? What are the eccentricities and inclinations of the orbits? Where would these new moons fit on the graph of orbits on the DTM’s website? Where did the names come from? Why are some of the more recent moons labeled “provisional”?
Using the data from one of the moon websites specified in question 2 show that P2/A3 is the same as it was for Io and Europa in Math Tools 11.1 (watch your units—P should be in days).
Go to the website for the Cassini mission ( Is Cassini still making observations? Look at a Cassini image of one of Saturn’s moons. What does this image reveal about Saturn? Watch the video at to listen to the “hiss” from the aurora. What moon is the cause of the aurora?
Do a search on “Europa mission” to see the status of proposed space missions to Europa. Have any of them been approved for funding? What will the mission study?

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