CEN 511: Recent Discoveris in Astronomy

Spring 2004

CEN511 # 3, DUE 17 FEBRUARY

If we don't cover the subject of the last question (galaxies) in class, it will not appear on February 17's quiz. However, we didn't cover much about the birth of stars in class and THERE WILL BE 1 question about this on the quiz. This subject will be covered at the beginning of Feb. 17th's lecture prior to the quiz. Also, you can ask questions about this problem before the quiz is distributed.

  1. Vega is a main sequence star, as is the Sun, but Vega has a luminosity about 50 times that of the Sun. Estimate the mass of Vega in units of the Sun's mass, and also estimate Vega's lifetime.
  2. The nucleus of He4 has an atomic number of 2. How many protons and how many neutrons does it have?
  3. C12 is formed in stars from the "triple-alpha" reaction. What is an "alpha" particle, and if 3 of them are combined into one C12 nucleus, how many neutrons and how many protons does C12 contain?
  4. C14 is radioactive. It decays when one of its neutrons changes to a proton and an electron. What nucleus is thereby created?
  5. Concerning how stars form:
    1. Why do interstellar clouds become warmer as they collapse to form stars?
    2. What eventually halts this collapse?
    3. Why does the rotation rate of a cloud increase as it collapses?
    4. What happens if the rotation rate becomes too large?
  6. Why do some stars explode as supernovae, while other stars just die out as cooling white dwarfs?
    1. What is the single property of a star at birth that determines which kind of death it will have?
    2. How long will a star at the boundary between these two kinds of death live?
  7. Where do most heavy elements come from?
  8. What are the major types of galaxies?
    1. What type of galaxy do we live in?
    2. What is the name of our galaxy?
    3. How many stars, roughly, are contained in our galaxy?
    4. What is the diameter of our galaxy?
    5. What is the thickness of the disc of our galaxy?
    6. What is the volume of the disc of our galaxy?
    7. What is the average density of stars in the disc of our galaxy?