1. What conditions are present in stars that cause hydrogen to form helium? What is this process called?
2. What are the major layers of the Sun? Which layer produces most of the light we see?
3. What two properties ofstars do scientists plot on a Hertzsprung-Russell diagram? Why do they choose these properties
4. Explain how supernovae produce neutron stars and pulsars.
5. How did Edwin Hubble discover that there are galaxies in the universe other than the Milky Way?
6. Why does the existence of the cosmic redshift lead to the big bang picture of the universe?
7. What is the cosmic microwave background and what role does it play in cosmology?
8. Describe Hubble's law. How did Hubble discover it?
9. What ef ect does dark energy have on the expansion of the universe?

Reflection Questions

1. Hubble Constant

Using the Hubble constant as shown to work calculations in the chapter,

1. Calculate the velocity that a galaxy is moving away from us if it is 300Mpc away?
2. Calculate the velocity that a galaxy is moving away from us if it is 200Mpc away?
3. Microwave Energy Maps
   1. Explain the significance of the microwave energy maps of the universe, such as the one produced by WMAP shown on page 338.
   2. How did these microwaves originate?
   3. Does the map show that the radiation is uniform? Explain the significance.

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