Astro101V: Midterm II


This is a take-home exam, and is due on or before Tuesday, Feb 23, 1999 AT THE BEGINNING OF THE CLASS PERIOD. This deadline is firm, and I will not accept exams handed in after 7:15 pm on Tuesday, Feb 23.

You may use your class notes, or information out of your own head, or the textbook, but using information out of other people's heads is bad form and WILL NOT BE TOLERATED. Remember that if I can't decipher what you've written, I can't give you any credit! Also, remember that a picture or diagram is often worth athousand words, and a thousand hours of thought...

If you have a question about the meaning of one of the questions, feel free to e-mail me: , or to call me in my office: (206) 543-2604. I may not be able to answer your question, but it's worth a shot.

Midterm II

  1. (5 points) What's a neutrino? Why are they important?

  2. (5 points) What property determines the fate of a star?

  3. (5 points) Why is an iron core unable to support a star?

  4. (5 points) Suppose that two white dwarf stars have the same surface temperature. Why is the more massive of the two white dwarfs the less luminous?

  5. (5 points) Suppose that AGB stars did not lose mass. What effect would this have on the number of white dwarfs in the galaxy?

  6. (5 points) Only a small percentage of the energy of a Type II supernova is carried away by radiation and the shell of matter blasted outward. What happens to the rest of the energy released in the explosion?

  7. (5 points) What effect do supernova explosions have on the chemical makeup of interstellar gas?

  8. (10 points) List the three forms of energy that are produced in the proton-proton process. What happens to each of these forms of energy?

  9. (10 points) Why are H and He the only primordial elements? That is, why were no heavier elements created in the Big Bang?

  10. (10 points) Where do you come from? (Please note that this question is worth ten points, and you are in astronomy class...)

  11. (15 points) Draw an H-R diagram. Label each axis using two of the following four terms on each axis: Temperature, Luminosity, I...III...V, O...A...M. Draw and label each of the following: Main Sequence, Red giants, White dwarfs, Blue giants, the Sun, Black dwarfs, the instability strip. What is the significance of this diagram?

  12. (20 points) It's the first week of summer, and you are lounging around on the beach in Mexico. The sun is high in the sky, you are peacefully baking, just dozing off, and listening to your favorite tunes on the radio. Suddenly, there is a loud burst of static on the radio, which dies down to a persistent low-level static hum. The radio station starts playing commercials in really loud Spanish. You crack an eyelid, reaching for the radio, and close it again as you grope for the tuning knob. Then your eyes fly open, and you sit up straight. There, near the Sun, is a brilliant spot of light, brighter than the moon!

    You realize that the radio is not broadcasting commercials, but excited announcements of this event. Your friend next to you picks up his head and blinks. "What's going on?" he says. You explain, pointing into the sky. His jaw drops. People are beginning to stand up and stare into the sky, and you notice that you have acquired a serious sunburn, even through your SPF 25 sunscreen. You grab your friend, and your stuff, and head swiftly to the hotel. You'd better stay inside for a few days, maybe even a couple of weeks or you'll be completely roasted.

    What happened?

    When did it happen (just now, a few days ago, a few months ago), approximately?

    Why are you sunburned, and what is the deal with the static on the radio?

    What are astronomers doing now?