The beginning of this activity was not created by me, but the manipulative extension for it was. In this activity the purpose is for students to categorize the star cards into similar groups. Students may choose to use Color, Luminosity, Magnitude, or Temperature. In the first sheet of the handout there are questions about how and why they grouped the stars the way the did. There are also follow up questions making relationships about all four categories. The second part of the activity has students placing stars on a large H-R diagram based on either their stars: Color, Luminosity, Magnitude, or Temperature. It really gives kids the idea that stars are classified by a variety of methods.