1) Suppose two stars, Castor and Pollux, have the same spectral line width, but Castor's peak wavelength is much shorter, giving Castor a blue color compared to Pollux. Assuming there is no interstellar material along the line of sight to either star and that the two stars have the same mass and composition, which star is larger (or are they the same size)? Explain your answer.

2) Suppose we wish to study a bright star in the constellation Cepheus. In order to do so, we'll need to correct for any effects of the interstellar medium (ISM) along the line of sight to that star.

a) (6 pts) Explain how and why spectral lines due to the ISM differ from stellar lines.

b) (8 pts) What is the approximate location (altitude and azimuth) of Cepheus at 10pm this evening? Also, what is the name of one of the bright stars in Cepheus? Finally, briefly explain (a single sentence will do) what Cepheus represents in mythology.

3) When we don't account for the effects of the interstellar medium (ISM) on a star we are observing, we will be unable to deduce the true properties of the star.

a) (6 pts) Briefly state how our estimates of apparent luminosity, temperature and absolute luminosity will differ from the true values for stars if we don't account for the ISM effects. No explanation needed.

Apparent luminosity estimate will be __________________ compared to true apparent luminosity.

Temperature estimate will be ________________ compared to true temperature.

Absolute luminosity estimate will be __________________ compared to true absolute luminosity.

b) (8 pts) One of the most interesting spectral features of interstellar clouds are forbidden lines. These are lines from certain elements that can only occur in a gas with an extremely low density. Explain why low density is necessary in order for atoms to emit forbidden spectral lines.

4) This question deals with two different types of interstellar clouds we studied in this part of the course.

a) (8 pts) What is the "galactic fountain" and what are two reasons that Astronomers feel Intermediate Velocity Clouds (IVC's) are part of the fountain process?

b) (6 pts) Why do molecules exist primarily in the cold, dense clouds we call molecular clouds and rarely elsewhere?

5) Star colors can sometimes tell us a lot about the properties of stars.

a) (4 pts) Why are red giants red?

b) (4 pts) Are all young main sequence stars blue? Explain your answer.

c) (6 pts) Why do we not see any green stars in the night sky?

6) Novae and gamma-ray bursts are among the brightest and most powerful explosions visible to us on Earth.

a) (7 pts) One source of gamma-ray bursts is thought to be magnetars. What is a magnetar? How was the source of the March 5, 1979 gamma-ray burst pinpointed?

b) (7 pts) Explain how nova explosions occur in binary systems.

7) Among the strangest of stellar remnants are black holes, about which we can only speculate their most important properties.

a) (7 pts) Explain how we "prove" the existence of black holes by monitoring motions in binary star systems.

b) (7 pts) If Alex were 100 miles away from the center of the Sun and Bob were 100 miles away from the center of a one-solar-mass black holes, which person would feel a stronger pull of gravity? Explain your answer.

8) Below is a graph on which you can draw a rotation curve. The standard Keplerian rotation curve has been draw in for reference. On the graph below, draw on what you expect the rotation curve of our galaxy would look like in the absence of dark matter. If you think it would just be the Keplerian curve, just write "SAME" on the graph.

To the right of the graph, explain your answer.