Version: 10 February 2012: This page will be updated after Tuesday's (14 February 2012) class (and in fact was revised at around 6 pm after class).

Version: 11 February 2012: I added Tests 1 and 2 to page.

Version: 15 February 2012: The review sheet was revised at the end of Tuesday's class around 6 pm.

Test 2, 16 February 2012
Astronomy 123

Material:Topic 3: Normal Galaxies (Final parts of Milky Way and normal galaxies, Topic 4: Active Galactic Nuclei (Chapters 24 & 25), Topic 5, World Views of the Universe (Chapters 26), and perhaps some of Topic 6, History of the Universe (Chapters 26 and 27), Observations and the Fate of the Universe (Chapters 24-26)

Old tests:

Test 1, Test 2

Normal Galaxies and the Milky Way Galaxy:
- There is a supermassive black hole at the center of the Milky Way galaxy. What is the mass of this Black Hole? Where is it in relation to Sgr A? What is a black hole? What are the properties of nonrotating black holes (Schwarzschild black holes) and rotating black holes (Kerr black holes). What is the Penrose mechanism? What is Cosmic Censorship?
- Sketch the structure of a black hole. What are the parts of a nonrotating black hole (Schwarzschild Black Hole): the Event Horizon, the singularity, the Static limit,the Schwarzschile radius? What are the corresponding parts in a rotating black hole (Kerr Black Hole)? In addition, what is the ergosphere?
- Contrast space and time outside the Event Horizon to inside the Event Horizon of a Schwarzshild black hole. If you are astronaut falling into a black hole, describe the journey from your perspective. What about from the point of view of someone watching a great distance?
- What are the properties of the black hole at the center of our Galaxy? Roughly what are the rates the black hole in the center of our Galaxy must eat stars to supply its energy needs? What about for Seyferts? What about for the most luminous QSOs? What are S2 and S6? What is Sgr A? Where is Sgr A? What are tidal forces?
- What are Population I stars? What are Population II stars? What are Population III stars?
- What is a tidal force? How do the effects of the tidal force compare (how are they different) for a small black hole compared to a supermassive black hole?
- What are galactic rotation curves (what kinds of rotation curves did I discuss in class)? What is the significance of the fact that most rotation curves are nearly flat at large distances from the centers of the gaalxies (the galaxy spins at nearly the same speed at large distances as at small distances from its center)?
- How do the mass estimates from rotation curve affect the question of the amount of Dark Matter in our Galaxy?
- What are MACHOs? Where are MACHOs found? How are MACHOs detected? (What is gravitational lensing?) What fraction of the Dark Matter is contained in MACHOs? Describe the MACHO experiment.
- Sketch the Hubble Tuning Fork diagram, be sure to include schematic representations of ellipticals, spirals, barred spirals, S0s & SB0s (lenticulars), and Irregulars, By schmeatic, I mean indicate the flattening of ellipticals, bulge sizes, and the tightness of the winding of spiral arms. Hubble Galaxy Classification scheme (24.1) Is the Hubble Tuning Fork diagram an evolutionary sequence? (Do galaxies evolve from one Hubble class to another?)
- What is the extragalacitc distance ladder? What is the Tully-Fisher method (how does it work)? How do Cepheid variables fit into the extragalctic distance ladder? How can Cepheids be used to determine distances to nearby galaxies? What are the most important ways to determine distances to distant objects? How do Type Ia Supernovas fit into the extragalactic distance ladder? What is meant by bootstrapping? How do we find distances to objects in our Solar System? How do we find distances to nearby stars?
- Why do objects cluster in the Universe? Describe the different clustering scales found in the Universe. How do we reconcile the inhomogeneity and nonisotropy of the Universe shown by the clustering with the Cosmological Principle? Can we reconcile the observed structure of the Universe with the CMBR? Explain your answer.
- Describe the properties of rich clusters of galaxies such as Virgo and Coma. Why are there no spirals found near the centers of rich clusters of galaxies? What are cD galaxies? Why are supergiant Elliptical galaxies often times found near the centers of rich clusters of galaxies? Why are galactic clusters thought to be common? Are they common? What fraction of galaxies have apparently undergone mergers over the lifetime of the Universe?
- What is meant by look-back time? What is meant by distances to objects can be ambiguous, why? The look-back time as it concerns distances to objects can be misleading, why? What is a more well-defined way to describe the location of distant objects in the Universe?
- What are voids, filaments, and the Sloan Great Wall? How large are they? How were these features detected?
- How does the observed structure of the Universe help to determine how much exotic dark matter compared to normal matter must exist in the Universe?
Active Galactic Nuclei (AGNs)
- Describe the different families of bright AGNs. Which class is the most luminous? Which classes are found in normal galaxies (or are all AGNs found in normal galaxies)? Which have the largest redshifts on average? Which have the smallest redshifts on average? What important properties of AGNs can we deduce from this difference in average redshift between Seyferts, radio galaxies and QSOs?
- What are the three observed features of AGNs which make them difficult to understand? (what do mean by nonthermal radiation? What objects can produce thermal radiation? How are the size of AGNs deduced? Why were QSOs (when first discovered in the 1960s) so difficult to identify? How are distances to most QSOs inferred? What are the relative brightnesses of AGNs (compared to normal galaxies)?
- Are AGNs totatly bizarre objects that are considered to be outside the realm of normal galaxies or are they considered to extreme examples of normal galactic evolution or what? Upon what evidence is your answer to the preceding question based?
- How can the Hubble Law used to determine the distance to a galaxy?
- What model is used to explain the efficient energy production of AGNs? What evidence supports our picture of the energy engines of AGNs?
- What are supermassive Black Holes? Describe the evidence that the Universe contains supermassive Black Holes. Describe the supermassive Black Hole in the nucleus of our Galaxy. How are supermassive Black Holes thought to be produced? How efficient are black holes as energy engines? What fuels the black holes found in AGNs? What is the radius of 1 billion Solar mass black hole? Describe the relationship between supermassive black holes and the bulges of the galaxies in which they are found. What is the significance of this relationship?
- Describe the relationship between supermassive black holes and the masses of the bulges of the galaxies in which they are found. What is the significance of this relationship? Why do AGNs turn-off as they age?
Models for the Universe
- Olbers's Paradox concerns the darkness of the night sky. Explain the nature of the paradox, that is, state the assumptions used, and outline the argument which leads to the conundrum. Explain how the Big Bang theory leads to the resolution of Olbers's paradox. (Be explicit in terms of how the paradox is resolved--on a broader note, in general, how does resolve any paradox?)
- Lemaitre and Friedman first solved Einstein's equations to determine the structure of the Universe. Lemaitre is referred to as the Father of the Big Bang. What assumption underlies Friedman's models for the Universe? List the types of Friedman models for the Universe. Describe each solution geometrically.
- In terms of their shapes (spacetime structures), describe each of Friedman's models for the Universe. In what type of Friedman universe are we thought to live? Which universe is a closed universe (and what does this mean)? Which universe is an open universe (and what does this mean)?
- How can we distinguish open, closed, and flat universes? Describe the tests and the results of the tests described in class. Describe the behavior of parallel lines, triangles in the different Friedman models. What astronomical objects have been used to perform these tests?
- What dynamical tests can we apply to determine the type of universe it is in which we live? What do we mean by dynamical test?
- What topological tests can we apply to determine the type of universe it is in which we live? What do we mean by topological test?
- What other class of test has been used to determine the type of universe it is which we live? Describe these tests.
- Describe the observation which gave the first credible evidence that the expansion rate of the Universe is increasing with time. What important result follows from the increasing expansion rate of the Universe?
History of the Universe
- How old is the Universe? How can we estimate the age of the Universe? How old are the oldest stars in the galaxy? (What objects are we referring to? Is there a problem with this age for the oldest stars?
- Sketch Hubble Law for nearby galaxies. Indicate how the Hubble Law changes for universes which are speeding up, slowing down, closed universes, open universes.