Learning Goals

Studying this chapter will enable you to

	Describe the basic properties of the main types of normal galaxies.
	Discuss the distance-measurement techniques that enable astronomers to map the universe beyond the Milky Way.
	Describe how galaxies clump into clusters.
	State Hubble’s law and explain how it is used to derive distances to the most remote objects in the observable universe.
	Specify the basic differences between active and normal galaxies.
	Describe the important features of active galaxies.
	Explain what drives the central engine thought to power all active galaxies.