If the spiral density wave were the only thing producing spiral arms, it would be expected that ...

If the spiral density wave were the only thing producing spiral arms, it would be expected that
 
  a. all spiral arms would be gas and dust free.
  b. all galaxies would have only two smooth spiral arms.
  c. the Milky Way would show and irregular pattern of short arms .
  d. the Milky Way wouldn't have any spiral arms.
  e. the halo component of the Milky Way would show spiral arms as well.

Question 2

What information can we get from eclipsing binaries that we cannot get from visual binaries?
 
  What will be an ideal response?

Question 3

Good tracers of the spiral arms of our galaxy are all I. very old. II. very young. III. very luminous. IV. moving with large radial velocities.
 
  a. I & III
  b. I & IV
  c. II & III
  d. II & IV
  e. I, III, & IV

Question 4

What measurements are needed to determine the orbital motion of a spectroscopic binary star?
 
  What will be an ideal response?

Question 5

The first stars to form in our galaxy
 
  a. had circular orbits.
  b. had highly elongated elliptical orbits.
  c. were population I stars.
  d. all had orbits in the same plane.
  e. formed the galactic clusters we see today.