The activity will display the planets motion around the sun.

1. Open Stellarium and hide the ground using the ground button from the bottom control bar or the shortcut key [G].
   
2. Turn off the atmospheric effect to have dark sky by using the shortcut key [A] or theatmosphere from the bottom control bar.
   
3. You should now see stars. Open the search dialog window from side bar or use the shortcut key [F3].
   
4. Search for “solar system observer”. Hit enter when it shows in bold
   
5. Press Ctrl+G (command+G on a mac). this will take you to a distant vantage point which is about 334 AU from the solar system.
6. Open the search dialog window again and search for sun. Hit enter when it shows in bold
   
   Now you are looking “down” on the solar system plane.
7. Open the sky and viewing options dialog window from side bar or use the shortcut key [F4].
   
   1. Under the “Sky” tab, match the settings shown below.
      1. In the Sky section, un-check the “Dynamic eye adaptation”
      2. In the “Solar System Objects” section,
         check “Show planet markers”
         check “Show planet orbits”
         check “Show planet orbits only”
         drag the “Labels and Markers” slider all the way to the right. This will show the labels of the faintest planets.
         
8. Close the sky and viewing options window.
9. Zoom in until the orbit of Mercury fills the screen. Note the position of the planet Mercury on your computer screen with tape or a Post-It note.
10. What is the date? (Look in the Information bar at the bottom of the screen) Enter this date as the Start Date for Mercury on your lab sheet.
    
11. Now press L a few times to speed up time (start with 4 or 5 times, don’t go too fast). You should see Mercury moving in its orbit, one day at a time, as it goes around the Sun. Press 7 to stop Mercury when it returns to its original position, which you marked on screen. If you missed the point step time forward and backward by one day at a time (using the – and = keys), to get the planet back exactly to where it started.
12. On the lab sheet, record this date as the End Date for Mercury.
13. How many days passed between Mercury’s Start Date and Mercury’s End Date? For ease of calculations you may assume 30 days to each month. The result is Mercury’s Orbital Period, T, measured in days.
14. Record. Repeat for all the other planets.

Follow the same procedure for the other planets. The further you get from the Sun, the slower the speed of the planets. Enter all your data in the table.

For each planet, calculate its orbital period in days, just as you did for Mercury. If a planet takes from September 5, 2015 until January 21, 2018 to go around the Sun once, that would be two years, four months (to make things easier, just assume that each month has 30 days) and 16 days, or 365+365+30+30+30+30+16 = 866 days. Enter the results for Orbital Periods in the table.

Now convert each planet’s Orbital Period from days into years, by dividing the Orbital Period from Table 1 by 365. Enter the result for each planet in the column – Orbital Period in years.