1. Review Questions for Exam #2

2. In order to figure out the mass of a star we observe binary star systems and use Kepler’s 3 rd Law, (M 1 + M 2 ) P 2 = 4π 2 *a 3 /G Discuss how we determine, P and a. How do we solve for individual mass (like M 1 ) rather than (M 1 + M 2 )?

3. Sketch an H-R diagram. Label the axes and indicate the direction of increase along each axis. Draw in the location of the main-sequence, super giants (I) the giants (III) and the white dwarfs. On the main-sequence, indicate with an arrow the direction of increasing mass. Given the arrow that you have drawn, how are luminosity and mass related on the MS and why? Put a big “R” in the place where on the diagram where the radii are the biggest. Put a “r” where the radii are the smallest. Given the relation L = σT 4 (4πR 2 ) explain why the “R” and “r” are at the locations you have labeled

5. Here is an image near the center of the Orion nebula, a star forming region. Explain what is happening in this picture Explain how this is related to the process of self-sustained star formation in the molecular cloud.

6. Fe

7. Discuss how the absorption lines form. What has to be true about the electrons in order to create absorption lines? What do the strength of the absorption lines depend on? In the spectra below, the temperature is the same for all three spectra. Why are the lines different strengths?

8. Explain what is happening to the proto-star as it follows the track below.

10. Explain this diagram What is going on at #1, #2, #3, #4? In #3 what is happening on the outside of the star? Why? #1 #2 #3 #4

11. Explain why a high mass core cannot get energy out of fusion of Iron. What happens to the core of a high mass star when it becomes iron? How does it produce a supernova?

12. Explain why a neutron star spins incredibly fast. How do we know that neutron stars really do spin rapidly? What objects show us that neutron stars spin fast? How does this object work?