The bottom of the dome represents the horizon. Preparing your class for a visit to the Planetarium Teachers please go over the material below which would be appropriate for your class before you bring your class to the planetarium. Light year is the distance that light travels in one year. How to measure angles . Stars - emit their own light because they are hot.
Planets shine by reflected light and circle stars.
Galaxy - a large collection of stars. The Milky Way galaxy contains 100 million stars. It is 80,000 light years across. The sun travels around the center of the galaxy in 200 million years. Preferable have the teacher have the class sketch the Big and Little Dipper, including Polaris in their correct relative position before coming to planetarium.