Objectives: Galaxies

Chapter Objectives: The visible Universe contains billions of galaxies that collect together in clusters, superclusters, bubbles, and "Great Walls" that are the large-scale structure of our Universe. In this chapter we will describe the three main classes of galaxies: spiral, elliptical, and irregular galaxies. The differences between the galaxy types will be illustrated and the suggested reasons behind these differences will be explored. The clusters and superclusters of galaxies will be described and the effects of galaxy interactions and collisions in the crowded clusters of galaxies will be shown. The large scale soap bubbles, voids, and walls that appear in three- dimensional structural "maps" of our Universe will be introduced.

Chapter Skills: After studying this chapter you should be able to

  1. Describe the basic physical characteristics of spiral, elliptical, and irregular galaxies.
  2. Discuss the evidence for and the effects of interactions between galaxies.
  3. Distinguish between groups, clusters, and superclusters of galaxies.
  4. Describe the Local Group that our Milky Way galaxy belongs to.
  5. Give the evidences for the existence of Dark Matter and the suggested forms this matter may take.
  6. Describe the three dimensional large scale structure of the Universe and the methods by which such pictures of the Universe are constructed.
  7. Summarize the various distance scales used in the study of the Universe as a whole.
  8. Outline the history of the discovery that our Universe is expanding and the importance of Hubble's Law in present day astronomy.