2. How far from the center of the galaxy is the solar system? What else besides stars are in the galaxy?
3. Label the following where appropriate: spiral arms, disk, halo, bulge, globular clusters, galactic center
3. see text book for better pictures .
1. Traveling through empty space, starlight arrives at Earth unchanged. What happens to the spectrum we observe if there is a gas cloud (no dust) between us and the star?
1. If the universe were contracting instead of expanding, how would we know (what would the observations be)?
If the universe were contracting, the radial velocities of all the distant galaxies would be blue-shifted. Instead, we see that they are all red-shifted.
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