Astr 222 Final Exam Study Questions

Short Answer Questions

The final exam will list EIGHT short answer questions; you must pick SEVEN of them to answer. Each short answer should be a short paragraph or so in length, and they will be worth 5 points each. They will be similar to the ones given below:
  1. Describe how the appearance of a galaxy would change (in terms of apparent magnitude, angular size, surface brightness, and morphology) if we were to magically move it to higher and higher redshift. You don't need to give quantitative numbers, but describe qualitatively what is happening.
  2. Describe how the stellar populations in spiral galaxies differ from those in ellipticals, and how we can study these stellar populations when galaxies are too far away to see their individual stars.
  3. In a cosmological context, what is meant by "the era of recombination"?
  4. Write down the Friedmann equation, including all terms. Describe qualitatively what role each term plays in terms of the shape and expansion history of the Universe.
  5. Describe what we mean by the morphology-density relationship for galaxies, and explain why galaxies behave this way.
Also study the short answer questions given on the midterms (both the real midterms and the practice midterms). One or two of the short answer questions on the midterm WILL come from those lists.

Essay Questions

The final exam will list THREE essay questions, taken from the list below. You must pick TWO of them to answer, and they will be worth 15 points each. Your essays should be ~ 2-3 blue book pages in length; essays much shorter than that probably will not be giving enough detailed explanation to get full credit.
  1. Describe the early history of the Universe from inflation to recombination.
  2. Describe (in detail) 3 pieces of evidence for dark matter in the Universe (using evidence that we have discussed in class).
  3. Give plausible values for the cosmological parameters: age, H0, Omega(Matter), Omega(Lambda). For each, describe two pieces of evidence which supports the value you've given.
  4. Why couldn't the dark matter be all baryonic -- i.e., "normal matter" that just doesn't shine (say dark clouds of dust, for example). Give several reasons.
  5. Why does large scale structure and galaxy clusters in the Universe grow differently under different cosmological models? Describe the difference in how structure forms both between cold and hot dark matter cosmologies, as well as in cold dark matter cosmologies with different values for Omega(Matter) and Omega(Lambda). Explain how can we contrain the value of Omega(Matter) using observations of galaxy clusters and large scale structure.
  6. Describe how supernovae can be used to study cosmology: the physics behind the test, the observational data required, and the results of these studies.
  7. Describe three ways for getting the mass of a galaxy cluster, and what data you would need in each case. Do these methods give reasonably consistent answers? Why or why not?
  8. Describe the properties of spirals arms in disk galaxies. Explain the winding problem and how density waves work to solve that problem. Why would star formation occur preferentially in spiral arm?
  9.  Describe the structure of the Milky Way Galaxy. Be sure to talk about the properties and relative sizes of the different components of the Galaxy. Where is the Sun's location in the Galaxy? A sketch will probably be useful here!
  10. Describe the Great Debate. Make sure to explain and evaluate the arguments on both sides -- whose evidence was flawed, and why? How did Edwin Hubble resolve this issue?
  11. Describe how the merger of two spiral galaxies could produce an elliptical. Describe the important differences between spiral galaxies and elliptical galaxies (think about morphology, kinematics, gas content, etc), and explain how a galaxy merger could account for these differences.


There will be THREE calculation problems listed on the final; you must complete all three. Each answer will be worth 5 points. These problems will be similar to the ones listed below.
  1. A distant galaxy cluster has a velocity dispersion of sigma=800 km/s and a half-light radius of 120 arcminutes. It has a average recession velocity of 8000 km/s. How far away is it? Use the virial theorem to show that the mass of the cluster is ~ 5Rsigma2/G. Calculate the mass of the cluster.
  2. If you had a telescope that could detect objects down to mB=22, what is the maximum distance a galaxy could be at if you wanted to study its globular clusters (which have a typical luminosity of LB ~ 6x105 Lsun)?
  3. You are studying two galaxies which have both had Type Ia supernovae in them. The supernova in Galaxy 1 had a maximum brightness of mB=12, while the one if Galaxy 2 had a maximum brightness of mB=15.5. How much further is Galaxy 2 than Galaxy 1? You do not need to know the absolute maximum magnitude of supernovae Ia to answer this!
  4. Show how the Friedman equation can be used to derive the mass density of a flat universe without a cosmological constant. If H0=72 km/s/Mpc, what is the density?