Download ASTR 1120 STUDY GUIDE FOR MIDTERM III This guide is to aid

ASTR 1120
STUDY GUIDE FOR MIDTERM III
This guide is to aid you in preparing for the THIRD MIDTERM EXAM in class on Thursday, April
24, which covers class lectures #15-21 (and the corresponding reading sections in Chapters
19,20,21,22 in The Cosmic Perspective), and draws on the lecture material, clicker questions and
homeworks. You should be familiar with THE BIG PICTURE and the SUMMARY OF KEY
CONCEPTS for each topic in those chapters.
If you need help on this material, please come to the REVIEW SESSIONS on Monday, April 21 and
Wednesday, April 23 (Duane G125, 6:00-7:30pm, given by Abhishek) . We also encourage you to
seek out the TA Abhishek Keshav or Prof. Rosalba Perna, either during office hours or by
appointment.
The exam will consist mainly of short-answer questions (multiple choice and true-false), which you
will answer on a computer gradable sheet, and two essay questions. Please bring a number 2 pencil to
the exam! The exams are closed book, closed notes, and no calculators, cell phones, iPods, etc. You
will NOT need to memorize constants. You should, however, know how the various equations we
discussed depend on the relevant variables.
Review Topics/Questions
1. What are the various phases of the recycling that occurs in the Milky Way ? Make sure you
are familiar with all the phases of the cycle, and how we observe them, depending on their
temperature.
2. How does the Milky Way look at various wavelengths? Which wavelengths are mostly
absorbed and which ones are not?
3. The cosmic “distance ladder”: what are the various ways by which astronomers measure cosmic
distances beyond what is possible with parallax? Be sure to be familiar with the basic idea for
each of these methods.
4. Remember the relation between apparent brightness, luminosity and distance.
5. Where is the evidence for the presence of a supermassive black hole at the center of the Milky
Way coming from?
6. Hubble’s law: what is it? How was it discovered? What are its important implications?
7. Structure of a galaxy: know how to distinguish various galaxy types, and be familiar with the
main elements that make up a galaxy (i.e. disk, bulge, etc.). What types of stars are more
common in the disk of a spiral? And what about ellipticals? Which galaxies are bluer in color
and which ones are redder? Why?
8. How did galaxies form? What are the main differences between the formation scenario of a
spiral galaxy and of an elliptical galaxy?
9. How did astronomers at the beginning of the century learn that we are not at the center of the
Milky Way? Where is the solar system located with respect to the Galaxy center?
10. Active Galactic Nuclei. What are they? Where do we find them? What is responsible for the
large output of energy that we observe?
11. What is the “local group”? Can you mention at least three other galaxies (besides the Milky
Way) that are part of it?
12. What is dark matter? Where is the evidence for it coming from?