Review for Exam 3

Lecture 15: Black Holes Define escape velocity. What 2 parameters does the escape velocity depend on? Define black hole and event horizon. To what diameter would you need to compress the earth to make it a black hole? What about the Sun? How are time and light affected near a black hole? Why do black holes tear apart anything that comes near them? How are black holes created? What are their typical masses and diameters? What is the order of main sequence stars, white dwarfs, red giants, neutron stars, and black holes in terms of surface gravity?

Lecture 16: The Milky Way What does the appearance of the Milky Way in the sky tell us about its true shape? In what wavelength range do we see light from hydrogen in space? How can we measure ages of open clusters and globular clusters? How do their ages compare? How can we estimate an age for a star that is not in a cluster? With current technology, we can use parallax to measure distances for stars out to a maximum distance of ___ light years. What is a standard candle? What is it used for? What are examples of standard candles in the Milky Way? What are the locations in the Milky Way of globular clusters, open clusters, gas/dust clouds, most stars, and the Sun? What is the diameter of the Milky Way? How many stars does the Milky Way contain?

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?

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 each of these properties tell us about quasars? 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? What is producing most of the light from a quasar? Because of its sharp images, what part of a quasar can be seen by Hubble that ground-based telescopes cannot see?

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 matter in the universe is dark matter? What do we think dark matter is?

Lecture 20: The Structure of the Universe What 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? What does it tell use about the universe? How are galaxies distributed in the universe? Why was dark matter important for the formation of galaxies? Why did Einstein propose the Cosmological Constant? Why did he later think that he made a huge mistake in proposing it?

Lecture 21: The Birth of the Universe What was the first evidence for the Big Bang? What were 2 supporting pieces of evidence? 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?

Lecture 22: The Fate of the Universe How is the rate of expansion of the universe changing over time? How was this measured? 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?

Lectures 23: Life in the Universe Why is there no record of the early earth? How old is the earliest evidence for life? What was the age of Earth at that time? What did the Miller-Urey experiment demonstrate? 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?

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 from the star and the planet’s mass? Which method was used to find the first known planet outside of our solar system? What kind of star does it orbit? Which method was used to find the first known planet around another star like the Sun? Which 2 methods have discovered most of the planets found outside our solar system? How many planets have been found outside our solar system? Which method of searching for planets has a large participation by amateur astronomers?