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:

- Find the first and last position of the moon you are working with.
Write the time each postion was imaged next to its location.
- Subtract the time of the first moon position from the time of the last moon position. Record this time.
- Draw radii from the center of jupiter to the first moon position and the last moon position.
- You should now have an angle that you can measure. Measure this angle and record it on your paper.
- Repeat these steps for each of the moons
- 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

- What percent of the whole orbit (circle) is the angle you drew?
- How long will it take for this moon to complete one orbit? (What is the orbital period of your moon?)
- What other information would you need to figure out how fast your moon is moving?
- 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.
- 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.