PROF. SHAPIRO HOMEWORK #8 1. How did Shapley locate the center of our Galaxy? 2. What evidence do we have that the Galaxy rotates? AST 301 3. How do globular clusters differ from open clusters? Why do we believe that they are among the oldest objects in the Galaxy? 4. Why are Population II stars thought to have been formed earlier than Population I stars? 5. What are HII regions? Where are they found? Why do they have sharp boundaries? 6. Two galaxies of the same size are observed to have flat rotation curves at all radii. The rotation speed of Galaxy #1 is twice the rotation speed of Galaxy #2. If the mass of Galaxy #2 is 1011 Mo, what is the mass of Galaxy #1? 7. Suppose we observe the rotation curve of the Milky Way out to distances from the galactic center which are ten times further away from it than the Sun is, but find the speed of galactic rotation is the same as it is at the Sun's galactocentric radius. What can we conclude is the total mass of the Milky Way galaxy inside that outer radius? By what factor is the mass enclosed by a sphere of this larger radius larger than the mass enclosed by the Sun's orbit of the galactic center? Why is this an argument in favor of the presence of a lot of dark matter in the Milky Way?