Review Questions for Exam #2

In order to figure out the mass of a star we observe binary star systems and use Kepler’s 3rd

Law, (M1 + M2) P2 = 4π2*a3/G

Discuss how we determine, P and a.How do we solve for individual mass (like M1)

rather than (M1 + M2)?

• 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 = σT4(4πR2) explain why the “R” and “r” are at the locations you have labeled

• 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.

Fe

• 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?

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

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

• 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?

• 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?