Learning Goals

Studying this chapter will enable you to

	Describe the overall structure of the Milky Way Galaxy, and specify how the various regions differ from one another.
	Explain the importance of variable stars in determining the size and shape of our Galaxy.
	Describe the orbital paths of stars in different regions of the Galaxy, and explain how these motions are accounted for by our understanding of how the Galaxy formed.
	Discuss some possible explanations for the existence of the spiral arms observed in our own and many other galaxies.
	Explain what studies of Galactic rotation reveal about the size and mass of our Galaxy, and discuss the possible nature of dark matter.
	Describe some of the phenomena observed at the center of our Galaxy.