Review for Exam 3

1. Review for Exam 3

2. Review • Exam: 50 questions, mostly multiple choice • Exam conducted at Pollock Testing Center • Each student schedules the time for their exam sometime between 8am and 10pm • Bring pencils and student IDs; no calculators allowed • For testing center details: http://testing.psu.edu/Students/ • Study materials • review questions • slides from lectures • your notes • homeworks • clicker questions • animations at my web site

3. Lecture 17: Galaxies • How do we classify galaxies? • What kinds of stars do elliptical galaxies contain? Spirals? • Do elliptical galaxies contain a large amount of gas/dust, or only a little? Spirals? How does that affect the kinds of stars contained in each kind of galaxy?

4. Lecture 17: Galaxies • How is the light from active galaxies different from light from normal galaxies? • What are the distinctive properties of quasars? • What does the rapid variability of quasars tell us about their energy source? What does their high redshifts tell us? • How can a normal galaxy become active? • How can we see what galaxies looked like when the universe was young? What were galaxies like when the universe was young? • How are elliptical galaxies created? • Why do ellipticals contain only old stars? • If you look at a quasar with Chandra, what is producing the X-rays that you detect? What additional aspect of a quasar can be seen with Hubble?

5. Lecture 19: Dark Matter • What are 3 pieces of evidence for the existence of dark matter? • How does each piece of evidence tell us that dark matter exists? • What percentage of all mass in the Milky Way is dark matter? • What do we think dark matter is?

6. Lecture 20: The Structure of the Universe • What types of stars are used as standard candles in measuring distances to galaxies? • What other methods are used for measuring distances to galaxies? Which method reaches the farthest distances? • How is the Tully-Fisher relation used for measuring distances? • What is the Hubble Law? • How are galaxies distributed in the universe? • Why was dark matter important for the formation of structure in the universe? • Why did Einstein propose the Cosmological Constant? Why did he later think that he made a huge mistake in proposing it? • What does the Hubble Law tell us about the universe?

7. Lecture 21: The Birth of the Universe • What are 3 pieces of evidence for the Big Bang? • According to the Big Bang theory, what is the cause of the redshifts of distant galaxies? • What temperature characterizes the microwave background today? How does that temperature change with time? • If the universe is dominated by gravity, how should the rate of expansion of the universe change over time? • How do we measure the age of the universe? • What is the observable universe? • What is inflation? • What was the age of the universe when hydrogen fusion ceased? • What was the age of the universe when the microwave background was emitted?

8. Lecture 22: The Fate of the Universe • How is the rate of expansion of the universe changing over time? How was this measured? • What is dark energy? How do we know that dark energy exists? • How did the amounts of radiation, matter, and dark energy compare immediately after the Big Bang? How do they compare now? • What is the age of the universe? • What is the shape of the universe? Does the universe have a center or an edge? • How does the shape of the universe depend on the density of matter and energy?

9. Lectures 23: Life in the Universe • Why is there no record of the early earth? • How old is the earliest evidence for life? • What is the Miller-Urey experiment? • What element is the basis for organic molecules? • What molecule is important for helping organic molecules combine into larger, more complex molecules (and life)? What other benefits does this molecule have for life? • What is the habitable zone? • Why are very large and very small planets unlikely to support life? • The presence of which element in a planet’s atmosphere may be evidence for life?

10. Lecture 24: Alien Worlds • What are the 6 methods of searching for planets around other stars? • Which 3 methods are used to detect the wobble of a star? • How does the velocity of a wobbling star depend on the planet’s distance and mass? • How was the first planet outside of our solar system discovered? What kind of star does it orbit? • Which method has discovered the most planets? • How many planets have been found outside our solar system? • Which method of searching for planets has a large participation by amateur astronomers?