Astr 222 Midterm Exam 2 Study Questions

Short Answer Questions

(There will be five short answer questions total on the midterm, worth 5 points each. They will be similar in style to the ones below.)
  1. Describe the general properties of starburst galaxies and explain how these starbursts might be triggered.
  2. You are studying a galaxy cluster whose distance you have determined from its redshift, and you calculate a virial mass of 1015 Msun for it. How and why does your answer depend on the Hubble constant? If the Hubble constant was actually 20% larger than you thought, how would your answer for the mass change?
  3. Sketch and label what's going on in the inner regions of an active galactic nucleus.
  4. Describe Cepheid stars and explain why they are important for studying galactic structure.
  5. Describe the evidence for a black hole at the center of our galaxy. Roughly how massive is this black hole?
  6. Describe  how the population of galaxies in clusters appears to have changed over time. Why might these changes have occurred?

Essay Questions

(One of the following essay questions will be on the midterm, and be worth 15 points.)

  1. Describe the Microwave Background: what it is, the physics behind it, and what it tells us about the Universe.
  2. Describe the unified model for quasars and active galaxies. How does it explain differences between Type I and Type II Seyferts? What differences between active galaxies does it not explain?
  3. Describe the Tully-Fisher relationship and the Fundamental Plane. What quantities are involved, and what types of galaxies do they describe? What do they tell us about the mass-to-light ratio of galaxies, and how can they be used to obtain distances to galaxies?
  4. Describe three ways for getting the mass of a galaxy cluster, and what data you would need in each case. Do these three method give reasonably consistent answers? Why or why not?
  5. Write down the Friedmann equation, including all terms. Describe qualitatively what role each term plays in terms of the structure and evolution of the universe.
  6. Describe the properties of spiral arms. Explain how density waves work, and how they solve the winding problem. Why would star formation occur preferentially in spiral arms?
  7. Describe several different lines of evidence that indicate we have a massive black hole at the center of our galaxy.
  8. Describe how the merger of two spiral galaxies could produce an elliptical. Think both about the shapes of galaxies and how stars orbit inside them. Explain how a galaxy merger could transform some of the cold gas we see in spiral galaxy disks into the hot gas in an elliptical galaxy halo.


(There will be two calculation problems on the exam, worth 5 points each. These are not the actual problems, but they will be similar....)