This lab was developed by the Project CLEA group at Gettysburg College, who have developed a whole host of computer-based astronomy labs. You will need to print out a copy of the .pdf Lab Manual for this lab and read over it first.
After you have read through the Student Manual for The Revolution of the Moons of Jupiter, read this material for some supplemental information and some specific changes.
The program may not have an icon on the desktop of your computer. If not, to start the program go through the Start Menu: Start à Programs à CLEA Exercises à Jupiter Moons. To log into the program, select FILE à LOG IN and enter your information. To begin making measurements, select FILE à RUN…. Make measurements over a period of 20 days, observing once every 24 hours. (It should default to this.) Record your results in the table on page 9 of the manual. Record the positions of Europa, Ganymede and Calisto, but not Io. (Io orbits too fast to map its motion well with observations once every 24 hours.) Despite what is says on page 8, DO record cloudy days in the table. You will not be able to record numbers, so just write “cloudy” in the cells for those days. This will keep you from skipping gaps that are actually in your data and mis-measuring the periods. As you make your measurements, use the highest zoom for which the moon is still in view. (This will probably be different for different moons and on different days. You will need to switch back and forth between zooms.) If a moon is not readily visible, it may be in front of Jupiter. If it’s not visible at all, it is behind Jupiter, and you know its position is within ½ a Jupiter diameter from Jupiter. After you have 20 days of observations, explore the “Top View” and “Animation” features of the program. (FILE à PREFERENCES à…)
Once you have your data, chart the moons’ motions using the graphs on pages 14 and 15 of the manual. Pay particular attention to the information in step 3, page 10, especially the information in italics. It is very unlikely that you will observe the moons exactly at their greatest distances from Jupiter, so you will have to fit your sine waves carefully to get accurate results.
Do not answer the questions on pages 12 and 13 of the manual. Instead, answer these:
Questions
1. Using the mass of the Sun as 1.989x1030 kg, use your average value for the mass of Jupiter (in solar masses) to find the mass of Jupiter in kilograms.
2. Compare (% error) your mass with the known mass of 1.90x1027 kg.
3. The Moon orbits the Earth once every 27.3 days at an average distance of 384,000 km. Use this information to find the mass of the Earth in kilograms.
With your report, turn in your data table and the graphs on pages 14 and 15.