29:62 General Astronomy
Big Book of Exam Questions
May 10, 1999

Omnis, in exitu eius, pulchrima denique visa est

All problems are worth 10 points. Write legibly, preferably in pen and in complete, well thought-out sentences.

1. What is the age of the universe? Describe the observations which indicate the value you have chosen.
2. A galaxy is observed to be receding from us at a speed of 10,000 km/sec. How far away is it? How does the distance to this galaxy compare with that to other objects discussed in the sections on extragalactic astronomy?
3. After finishing this course, you go home and begin looking at the sky with the aid of your SC1 chart. You find the star Virginis in the evening sky. How would you go about (i.e. what kind of observations would you propose) to determine what kind of star it is, i.e. like the Sun, not like the Sun, etc. While you are meditating on this, your kid sister comes up and asks you if there could be people on planets around that star. What kind of stellar characteristics would bear on the answer you give to her? Confession: Yea, I know this isn't over the last part of the course, but it is such a great question I couldn't help asking it.
4. Here's a perennial favorite: Suppose that ten years from now you read an article in the New York Times, stating that astronomers have discovered a star cluster which is 50 billion years old. What would be the implications of this discovery for our understanding of cosmology? Your discussion should place this result in the context of the lectures and reading material on cosmology.
5. A radio telescope points in the galactic plane at a longitude of and makes spectral observations. There are two hydrogen clouds along the line of sight, one at a distance of 7 kpc from the galactic center, the other at the tangent point. Draw the spectrum which would be observed.
6. In class I discussed the scalar curvature R of the universe. There are two possibilities for how R depends on time. Sketch these, and discuss what physical parameter (or parameters) determines which possibility will occur. Which represents the universe in which we live?
7. Roughly how far away are some of the nearest galaxies outside the Local Group?
8. What is meant by the Local Group?
9. Define what is meant by the term Dark Matter. What observational evidence is there for its existence?
10. Describe an observation which shows that the Big Bang occurred.
11. The brightest stellar objects are Type I supernovae, which have an absolute magnitude of -20. What is the velocity with respect to us of a galaxy in which such a supernova appears at apparent magnitude +20.
12. Luminous radio galaxies such as 3C79 and 3C430 all have a similar structure. Draw an annotated diagram of the radio emission in a radio galaxy, with correct dimensions.
13. What is the radiation process through which radio galaxies and quasars produce their emission? What is the source of the energy of radio galaxies and quasars?
14. A spectral line with a rest wavelength of 400 nm appears in the spectrum of a quasar at a wavelength of 1000nm. What is the velocity with which the quasar is receding from us? What is its distance?
15. Describe in about one page the topic in this course which interested you most. You will be graded on the clarity of your description of the issues involved, the physics content, and the relevant observations.
16. One of the people on Psychic Hotline says that the large spiral galaxy NGC 253 has a mass . What would be the orbital speed at a distance of 50 kpc from the galactic nucleus (assume that this is the most distant point at which a velocity measurement is made).
17. In class we discussed rotation curves of galaxies. Using knowledge gained in this class, discuss what kind of observations you would make to measure a rotation curve.
18. You are back home for the summer. A High School friend of yours, knowing you have taken an astronomy course, asks what is the most distant object we know of. Give your response, describing what the object is and how we have determined its distance. It is not necessary for you to come up with the absolute record holder, but choose one of the most distant objects. A generic class is OK.
19. Draw a diagram showing the size and shape of the Milky Way galaxy. Draw an X with ``Standort'' at the position of the Sun. Where are the young stars found (not James Dean, Rock Hudson, etc; stars like we have been talking about)?
20. Make a rough drawing of the rotation curve of the Milky Way galaxy, with proper numerical labels for the axes. What is the primary astronomical deduction which may be drawn from this rotation curve?
21. Describe the observed properties of quasars. What are they (i.e. stars, planets, molecular clouds, galaxies, etc)?
22. Put together some ideas developed in class and describe how we might infer from observations how long it took after the Big Bang for galaxies to form.
23. How old is the universe? Describe how we know this, i.e. what observations do we use to come up with this number.
24. What is Hubble's Law? Be quantitative. What is the physical significance of the Hubble constant?
25. In a Friedmann universe, what determines whether the universe is open or closed?
26. What is the Cosmic Background Radiation? What is its significance for cosmology?
27. Describe an astronomical observation or measurement which indicates that the energy source of radio galaxies lies in the centers of these galaxies.
28. There is a compact radio source at the center of the Milky Way galaxy. Discuss the feasibility of directly measuring the rotation of the Milky Way by measuring the shift in angular position of this source against background extragalactic radio sources. If it is feasible, describe what kind of instrument would be used. You are expected to know roughly the galactic parameters necessary to carry out this calculation. You will probably find it easier to clearly express your ideas by using diagrams. Note: 1 year = seconds.

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