1. How does a white dwarf differ from a neutron star? How does each form? What keeps each from collapsing under
2. How is a nova different from a type Ia supernova? How does it differ from a type II supernova?
3. What do astronomers think are the causes of longer-duration gamma-ray bursts and shorter-duration gamma-ray bursts?
4. Explain why we see the Milky Way as a faint band of light stretching across the sky.
5. Explain why the abundances of heavy elements in stars correlate with their positions in the Galaxy.
6. Suppose somebody proposed that rather than invoking dark matter to explain the increased orbital velocities of stars beyond the Sun’s orbit, the problem could be solved by assuming that the Milky Way’s central black hole was much more massive. Does simply increasing the assumed mass of the Milky Way’s central supermassive black hole correctly resolve the issue of unexpectedly high orbital velocities in the Galaxy? Why or why not?
7. Describe the main distinguishing features of spiral, elliptical, and irregular galaxies.
8. Why can we not determine distances to galaxies by the same method used to measure the parallaxes of stars?
9. According to Hubble’s law, what is the recessional velocity of a galaxy that is 100 million light-years away from us? (Assume a Hubble constant of 22 km/s per million light-years.)
10. Describe at least two characteristics of the universe that are explained by the standard Big Bang model.
11. What is dark energy and what evidence do astronomers have that it is an important component of the universe?
12. It is possible to derive the age of the universe given the value of the Hubble constant and the distance to a galaxy, again with the assumption that the value of the Hubble constant has not changed since the Big Bang. Consider a galaxy at a distance of 400 million light-years receding from us at a velocity, v. If the Hubble constant is 20 km/s per million light-years, what is its velocity? How long ago was that galaxy right next door to our own Galaxy if it has always been receding at its present rate? Express your answer in years. Since the universe began when all galaxies were very close together, this number is a rough estimate for the age of the universe.
