Analyze the Information

With your new perspectives in hand of each of the moons' orbits, let's see what we can find out about their orbits. Get your protractor and ruler handy.

Gather Some Data

For each of the drawings you made do these steps:

• 1. Find the first and last position of the moon you are working with. Write the time each postion was imaged next to its location.

  2. Subtract the time of the first moon position from the time of the last moon position. Record this time.

  3. Draw radii from the center of jupiter to the first moon position and the last moon position.

  4. You should now have an angle that you can measure. Measure this angle and record it on your paper.

  5. Repeat these steps for each of the moons

  6. Use a ruler to measure the radius of Io's orbit in centimeters. Also measure the diameter of the planet Jupiter (the circle in the center) in centimeters.

Do Some Math

• 1. What percent of the whole orbit (circle) is the angle you drew?

  2. How long will it take for this moon to complete one orbit? (What is the orbital period of your moon?)

  3. What other information would you need to figure out how fast your moon is moving?

  4. You have measured the orbital radius of Io and the diameter of Jupiter on your plate model, both in centimeters. The actual diameter of Jupiter is 142,984 km. Use a simple proportion with these numbers to calculate the actual radius of Io's orbit in kilometers.

  5. You now have determined Io's period and orbital radius. Locate a source for the published values for these quantities to see how close you came.