We’re just a few weeks past the vernal or spring equinox, so let’s think about the seasons. Spring is a time of renewal and growth: we start to see plants peeking through the soil, trees budding, bird songs filling the sky during the day, and frog songs at night. We are familiar with seasonal changes in our surroundings, but why do seasons change in the first place? Are there any seasonal changes you might not have noticed?

Curiosity Challenge: Use Stellarium to observe the Earth’s motion around the Sun. Discover why we experience different seasons. Check out what is visible in the night sky at 11 pm on different dates throughout the year.

Adjusting Stellarium Settings:

1. Download and install Stellarium onto your computer
2. Launch the program
3. Press F4 to bring up the sky and viewing options window
4. In the Sky tab, uncheck the boxes for:
   • Milky Way brightness/saturation
   • Dynamic eye adaptation
   • Atmosphere visualization
   • Stars
5. In the SSO (solar system objects) tab, check the boxes for:
   • Show orbits
   • Only orbits of major planets
   • Only orbit for selected object
   • Show planet markers
6. Click on the X in the top right to close the menu

Exploring in Stellarium:

1. Press F3 to bring up the Search window
2. Search for “solar system observer” and press Enter
3. Press Ctrl + G – this will bring you to a point in space where you can observe the solar system
4. You can zoom in and out using the scroll wheel of your mouse and move your viewpoint by left clicking and dragging your mouse around
5. Move so that you can see the planet orbits as close to circles as possible
6. Click on Earth – this will make all the other orbits disappear
7. The menu at the bottom of the screen will allow you to control time:
   •  = Rewind (each click speeds up time)
   •   = Play/Pause (toggles between the two)
   •  = Return to current date and time
   •  = Fast Forward (each click speeds up time)
8. Click on Play and set time speed so that you can see the planets orbiting the Sun
9. Click Pause at various times to see what the date is

Investigating Earth’s Orbit:

1. During which month is Earth closest to the Sun?
2. During which month is Earth farthest from the Sun?
3. Is this what you expected?
4. Press F5 to bring up the Date/time window. Set the date to March 20. Close the window. Look in the data for Earth in the top left of your screen to find the distance between the Earth and Sun.
5. Repeat this for June 20, September 20, and December 20. What do you notice?
6. Given your observations, is the distance between the Earth and Sun the reason for seasonal changes?

1. Restarting Stellarium will bring you back to the default settings.
2. Use the time window to set the time to 11 pm.
3.  These controls in the bottom left will allow you to display the constellation lines, names, and art, respectively. Turn on the name and the line and/or art.
4. Choose 4 constellations from around the sky noting in which direction you are looking to see them.
5. Move the date ahead 3 months and find your constellations. Are they all visible?
6. Move the date ahead another 3 months. Can you see your constellations now? 
7. Pick 4 new ones. Repeat the two previous steps.
8. Why do we not see the same constellations all year?
9. Did you see any of your constellations throughout the whole year? Which ones? Where are they located?
10. Constellations we can see year-round are called circumpolar. Press F6 to open the location window and change your location on Earth. Try going to the equator and the north pole. How does your location affect which constellations are circumpolar?