What are cataclysmic variable stars? List at least two types of this class of stars.
What is it difficult to determine the shape and size of our Galaxy? How does interstellar dust complicate these observations?
How did Shapley use globular clusters to determine the distance to the center of our Galaxy? Why was it necessary to use Cepheid variables to make these measurements?
Draw a diagram of our galaxy. Label the disk, bulge, and halo. Also label the dust, globular clusters, and the spiral arms. What is the diameter of our Galaxy?
What do spiral arms form? What types of objects are found in the spiral arms that are not found in the other sections of the Galaxy?
Why and how are bulge stars different from disk stars?