The final will contain 50 multiple choice questions, each worth 1 point, plus 10 short answer questions each worth 3 points, for a total of 80 points.

The final will test everything covered during the semester so far, but there will be an emphasis on material covered since the midterm.

Week 3: Sun

1. How much bigger is the Sun than the Earth: by radius; by mass; by volume?
2. Of what two elements, and in what proportions by mass, is the Sun mainly composed? How do we know that?
3. The density at the center of the Sun is about 160 times that of water, and the temperature at the center of the Sun is about 15 million Kelvin. What is the state of matter under these conditions?
4. Why does the Sun not collapse under its own weight?
5. By what two mechanisms does energy move through the Sun, from the center to the photosphere? Can you think of examples of the same kind of energy transport mechanisms in your everyday experience? Are there notable differences between the Sun and your example(s)?
6. Most quotable quote from Eddington's paper The Internal Constitution of the Stars.
7. Lord Kelvin suggested that the Sun might be powered by gravitational energy. Explain this idea, and why it fails.
8. What is the main source of energy generation in the Sun? Has mankind discovered a way to use this kind of energy? Why does the Sun not explode like a nuclear bomb?
9. Explain the difference between fusion and fission. What element contains no more nuclear energy?
10. Imagine that magically you could speed up one, and only one, nuclear reaction in the center of the Sun. Which one would you speed up in order to make the Sun shine most brightly? How much brighter would the Sun shine then?
11. What is helioseismology? What do we learn about the Sun from helioseismology?
12. How are solar oscillations measured?
13. What is the solar neutrino problem? What is now thought to be the solution of the solar neutrino problem?
14. Locate the website of a ground- or space-based observatory that is currently observing the Sun. Write a short paragraph describing the observatory and its mission.
15. What's the Space Weather like today? Does the Sun today have any spots? Why do x-rays from the Sun tend to forecast space weather around Earth?

Week 4: Stars

1. What is parallax? How do astronomers measure it, and what is it useful for?
2. What is a parsec, and what has it got to do with parallax? How many lightyears are there in a parsec?
3. Who or what is or was Hipparcos?
4. Do the shapes of the constellations change with time (even slightly)? Explain.
5. Sirius A, the brightest star in the sky apart from the Sun, is classified as A1V. What do the letters and numbers mean?
6. By what factor is the apparent brightness of the Sun brighter than Sirius A? (Find out the difference in apparent magnitudes, then figure out what factor that corresponds to).
7. Of the 25 stars nearest the Sun (excluding the Sun itself), what is the most common type of star? Are there any red giants? Are there any white dwarfs? Are there any binary systems? Are there any stars just like the Sun?
8. Who was Annie Jump Cannon, and what contribution(s) did she make to astronomy?
9. What is the main physical parameter that determines the color of a star? What else can affect its color?
10. Over what range of luminosities do stars range (in units of the Sun's luminosity)? What kind or kinds of stars are the most luminous? What kind or kinds of stars are the least luminous?
11. What measurements must astronomers make in order to determine the radius of a star?
12. In what ways do clusters of stars prove useful to astronomers?
13. In a binary star system, what information is needed to measure the sum of the masses? What information can be used to measure the ratio of the masses?
14. In this binary star simulation (linked on the Stars->Binaries page of the hypertext), what do the moving black lines on the spectrum signify? Is there anything wrong with this simulation?
15. In this eclipsing binary simulation (linked on the Stars->Binaries page of the hypertext), why is one of the two eclipses deeper than the other? When do the light curves of the eclipses have flat bottoms?

Week 5: Stellar Evolution

1. The main sequence is a sequence of what?
2. Why are most stars found on the main sequence?
3. What limits the maximum possible mass of a main sequence star?
4. What happens in the core of a star when it runs out of hydrogen at its center, and how does the star as a whole respond?
5. A main sequence star like Sirius A, with a mass of 3 solar masses, is expected to end its life as a white dwarf of perhaps 0.7 solar masses. What happens to the rest of the mass of the star?
6. Why do massive main sequence stars have lifetimes much shorter than the Sun's lifetime?
7. Explain how it is possible to measure how old a star cluster is from its Hertzsprung-Russell diagram.
8. Where are the oldest stars in the Milky Way found? About how old are they?
9. Give an account of the nature of the pressure that holds up a white dwarf star.
10. What is the connection between a white dwarf and the core of a red giant star?
11. What is a helium flash? In stars over what range of masses does a helium flash occur? What happens to a star as a result of a helium flash?
12. What is the triple alpha reaction? Why is the triple alpha reaction important to the existence of life?
13. On the Stellar Evolution->White Dwarfs page of the hypertext, there is a plot of radius versus mass, showing planets and white dwarfs on a blue line, and main sequence stars on a separate green line. What are the main sequence stars doing that planets and white dwarfs are not?
14. What is a planetary nebula? What has it got to do with planets?
15. What is the "Algol Paradox", and what is its solution?

Week 6: Novae and Supernovae

1. Which of the two does a nova more closely resemble, a thermonuclear supernova, or a core collapse supernova? Give an account of the various similarities.
2. In what way are supernovae important to the existence of the Earth and of life?
3. What causes a thermonuclear supernova to occur?
4. One of the clues that a thermonuclear supernova is a thermonuclear supernova is that the late time light curve of the supernova decays with a half-life the same as a certain radioactive element. What is this element, and what does it decay to? What is the half-life (do a search on the hypertext)? Suppose that a thermonuclear explosion occurred which incinerated the material until no nuclear energy was left. What element might you expect to be most abundant?
5. Do we know exactly what kind of binary system leads to a thermonuclear supernova? What do we think we know, and what remains uncertain?
6. Whereabouts in galaxies are Type 2 (core collapse) supernovae commonly observed? Why does this suggest that a Type 2 supernova represents the explosion of a massive star?
7. What has the Chandrasekhar limit got to do with a core collapse supernova?
8. Give an account of neutrinos in a core collapse supernova that produces a neutron star. Why must the supernova produce neutrinos? What do these neutrinos do?
9. Does a core collapse supernova always produce a neutron star? Can it produce a black hole?
10. What are the sources of energy of the two kinds of supernova, thermonuclear and core collapse?
11. What is special about Supernova 1987A? In what ways has Supernova 1987A helped astronomers' understanding of supernovae?
12. What is happening to Supernova 1987A today?
13. Find on the web a picture (or pictures) of the remnant of one of the historical supernovae (one that occurred before 1800). Describe what this picture shows. In what kind of electromagnetic radiation was the picture taken? By what mechanism does the remnant emit such radiation?
14. If a supernova went off in our Galaxy, the Milky Way, would we be able to see it with the naked eye? Could it be as bright as the brightest stars or planets? Could it be as bright as the Sun?
15. Check out the websites of the Supernova Cosmology Project or of the High-Z Supernova Search team. What remarkable thing in cosmology did observations of distant supernovae reveal in recent years (1998, to be precise)?

Week 7: Neutron Stars and Black Holes

1. Read Jocelyn Bell's account of the discovery of pulsars. Do you think that she should have won the Nobel prize instead of the person who actually got it? Present your arguments.
2. What evidence points to the Crab nebula (Messier 1) being the remnant of a supernova explosion that happened in 1054?
3. In what way was the Crab nebula important in clarifying the nature of pulsars?
4. There are some beautiful pictures of the Crab nebula on the web. Find one you like, and write down the url. What mechanism causes the radiation emitted by the Crab nebula?
5. In what ways does the binary pulsar PSR 1913+16 offer important tests of Einstein's General Theory of Relativity?
6. Look up the Laser Interferometer Space Antenna (LISA) website. Give a short description of LISA. When might it be launched? What are the principal science objectives of the mission?
7. Why are x-rays a good kind of radiation in which to search for neutron stars or black holes?
8. What is the relation between the Chandrasekhar mass and the observed masses of neutron stars? Does this support theoretical ideas of how a neutron star forms?
9. What observational evidence suggests that Cygnus X-1 contains a stellar-massed black hole?
10. In what way is an x-ray burster similar to a nova?
11. Find the website of a current or future x-ray or gamma ray mission (url please). Give an account of the mission and its objectives.
12. What is a gamma ray burst? What evidences indicate that gamma ray bursts come from cosmological distances and are therefore extremely energetic?
13. What is thought causes a gamma ray burst?
14. You watch a friend fall into a black hole. Describe what you see happen to your friend.
15. You fall into a black hole. Describe what happens to you.

Week 9: The Milky Way

1. For the mathematically inclined: how much bigger is the Milky Way than our Solar System? Compare these relative sizes to something more familiar. [For example, if the Milky Way were as big as the Earth, roughly how big would the Solar System be? As big as an atom? A marble? A human being? Boulder? The USA?]
2. Look at the Multiwavelength Milky Way (linked on the hypertext at Milky Way -> Introduction). Compare and contrast the appearance of the Milky Way at two different wavelengths of your choosing. What wavelengths did you choose? What causes the observed radiation at these wavelengths?
3. Give an account of Henrietta Leavitt's work on the Period-Luminosity relation. Read her 1912 paper on the subject (follow the links on the hypertext). Do we know what she thought about the issue?
4. Describe how the Period-Luminosity relation allows astronomers to determine distances to other galaxies.
5. What are globular clusters? How did Harlow Shapley measure distances to them? What did he infer from the distribution of globular clusters in the Milky Way?
6. Look at the Java simulator of rotation velocities linked at Milky Way -> Mass. Give a qualitative (not necessarily mathematical) account of how it is possible to measure the mass of an object by measuring how fast other objects orbit around it.
7. What is a "rotation curve" of a galaxy? How does the rotation curve of the Milky Way tell us about the presence of "Dark Matter"?
8. What is a MACHO? Have MACHOs been detected? How?
9. Do astronomers know the nature of the "Dark Matter"?
10. Look at the velocity-longitude map of carbon-monoxide (CO) in the Milky Way (bottom panel of the image at Milky Way -> Spiral Arms). How do astronomers determine the velocity? Is this velocity related to the "rotation curve" velocity described in Milky Way -> Mass?
11. Refer again to the maps of carbon-monoxide (CO) in the Milky Way at Milky Way -> Spiral Arms. Why is the velocity-longitude map more informative than the latitude-longitude map in determining the center of the Milky Way?
12. How do astronomers know that the Milky Way has spiral arms?
13. What is the astronomical name of the object observed at the very center of the Galaxy? Give the url of a site which presents observations of this object, and give a brief discription of the observations. [In what wavelength were the observations taken? What do the observations show? Do we understand the mechanism by which the object emitted? Was the object variable?]
14. Read about the latest observations of motions of stars about the center of our Galaxy at http://www.mpe-garching.mpg.de/www_ir/GC/ (linked on the hypertext at Milky Way -> Center). What do the observations reveal?
15. Which came first (which are younger): Population 1 or Population 2 stars? What does the difference in the distribution of these objects suggest about the evolution of the Milky Way?

Week 10: Star Formation

1. Photographs of star forming nebulae often show striking colors of red and blue laced with regions of black. What causes these different colors? [Note: Vigorous star forming regions such as Orion, as well as planetary nebulae, often show also a luminous aqua color. A hundred years ago this color was attributed to a mysterious element dubbed nebulium; eventually it was recognized as emission from doubly-ionized oxygen.]
2. What wavelengths of electromagnetic radiation tell us best about the various kind of insterstellar gas? Why?
3. What fills most of the volume of interstellar space? What makes up most of the mass of interstellar space?
4. Where does interstellar dust come from? What observational evidence indicates this?
5. Why does diffuse gas in interstellar space not collapse under its own gravity?
6. Paradoxically, for stars to form, it is necessary for gas to cool. Why?
7. Why can we not see newborn stars in optical light?
8. What is a proplyd? Where are they found? What are they doing?
9. In star forming regions such as the Orion nebula or the Eagle nebula, we see evidence for a process that will eventually stop any further star formation from occurring. What is this process?
10. What is the relation between star forming regions and an open cluster of stars, like the Pleiades?
11. There are many beautiful images of star-forming regions on the web. Find one, give the url, and describe what the image shows.
12. When was the first extrasolar planet found? How many extrasolar planets are now known? When was the most recent planet found?
13. What is the mission of the Terrestrial Planet Finder? When might it launch, maybe? The project may cost tens of billions of $$; do you think it's worth such a cost (how much would such a mission cost each person in the US)?
14. Besides the Doppler method, what other method has been used to detect extrasolar planets successfully?
15. What is a brown dwarf? In what way does it differ from a star or a planet?

Week 12: Galaxies and the Universe

1. What is a "standard candle" in astronomy? What makes (a) Cepheid variables, and (b) thermonuclear supernovae good standard candles for measuring distances to galaxies?
2. Historically, what was it that established that the "spiral nebulae" were "Island Universes", galaxies comparable in size to our own Galaxy, the Milky Way?
3. What is the Local Group of galaxies? Who are the principal galaxies of the Local Group? Are there members of the Local Group that orbit our own Galaxy, the Milky Way?
4. What is the Local Supercluster of galaxies? What is the cluster at the center of the Local Supercluster? Whereabouts is the Local Group within the Local Supercluster?
5. Explain how Hubble's law indicates that there was a Big Bang. How does Hubble's law tell us about the age of the Universe?
6. The galaxies in the Local Group do not follow Hubble's law (for example, the Andromeda galaxy is approaching Milky Way). Why do the galaxies in the Local Group not obey Hubble's Law?
7. How are galaxies distributed in the Universe? What physical cause produces this distribution?
8. Look at the movie of the spiral galaxy M81 (linked at Galaxies -> Types). Why does the appearance of the galaxy change during the movie?
9. What kind of astronomical objects are observed to act as gravitational lenses? What do such gravitational lenses reveal to astronomers?
10. What happens when galaxies collide? You might like to take a particular example on the web and describe it. (Do stars collide? Do the galaxies' shapes change, and if so why? Do the galaxies merge? What happens to the disks of spiral galaxies?).

Week 13: Active Galaxies

1. What is a DRAGN? What causes the radio lobes in a DRAGN?
2. What observation indicates that a quasar is very far away? Explain how it is that when we see a distant quasar, we are seeing it as it used to be a long time ago.

3. Quasars were most common "at a redshift of two", hundreds of times more common than they are today. What does "at a redshift of two" mean? Where have all the quasars gone?

4. Why can't the observed superluminal expansion of radio blobs in 3C273 be used to rule out Einstein's theory of relativity?
5. Can we say something about the size of an unidentified distant point-like object if we know that it varies on a time-scale of 1 day? Explain the reasoning.
6. What observational evidences point to the conclusion that AGN are powered by supermassive black holes?
7. Which is the most massive black hole known? How do we know its mass? (Look at this census of supermassive black holes, taken from Supermassive Black Holes in Galactic Nuclei by John Kormendy and Karl Gebhardt).
8. The best evidence for a supermassive black hole in a galaxy, besides the one in our Galaxy, is the one in NGC 4258 (aka M106). Give a brief account of the evidence for a black hole in NGC 4258.
9. What two distinct observational evidences indicate that cosmic jets are in many cases moving at close to the speed of light?
10. The picture captioned "M84" at the top right of the page Active Galaxies and Quasars -> Black Holes shows what appears to be a colorful whirlpool. Explain what the picture actually shows. (Warning: the hypertext explanation is not sufficient. Click on the picture to get to the HST website. The correct answer has something to do with the spectroscopic slit shown in the left image of the image on the HST website).

Week 14: Origin and Fate of the Universe

1. What observational evidence favors the Cosmological Principle? [Hint: there are at least two separate evidences, one of which is much better than the other. Which one is better, and in what sense is it better?]
2. In 1998, two groups searching for high redshift supernovae reported observational evidence for "Dark Energy". What was the observation? What is Dark Energy? Explain how the observations indicated the existence of Dark Energy.
3. The age t of the Universe is approximately equal to 1/H, the reciprocal of the Hubble constant. Why is this relation not exact? For a given Hubble constant (the best current value is 71 km/s/Mpc), explain qualitatively whether the inferred age would be lesser or greater in a universe with or without "Dark Energy".
4. How is the geometry of the Universe related to its mass-energy content? Does this relation remain valid if there is Dark Energy?
5. How old was the Universe when the epoch of Recombination occurred (for the most recent number, see the WMAP website)? What happened at Recombination? [Hint: quite a lot happened.]
6. The temperature of the cosmic fireball at Recombination was about 3000 Kelvin, whereas its temperature now, as inferred from the Cosmic Microwave Background, is about 3 K (2.726 Kelvin to be precise). What process has caused the temperature to decrease? From these two temperatures, what can be deduced about the size of the Universe now versus at Recombination?
7. What is meant by the cosmological horizon of the Universe? Is the Cosmic Microwave Background emitted from the horizon? What happens to the cosmological horizon as time goes by in (a) a decelerating universe, (b) an accelerating universe?
8. How do ripples in the Cosmic Microwave Background inform us about cosmology? Explore the WMAP website for details.
9. Comparison of the predictions of Big Bang Nucleosynthesis with observations leads to a measurement of an important cosmological parameter. What are those observations? What is the cosmological parameter, and what is the surprising result?
10. A friend asks, Does the Universe have an edge? If the Universe is expanding, what is it expanding into? Answer your friend as best you can.

Updated 2003 Apr 25