Dec. 10 Tuesday
FINAL EXAM, 12 in the noon (B112 Angell Bldg)
Dec. 8 Sunday Help
Session, 6-9 pm (Lafayette 108)
Dec. 3 Life in the Universe
H 1. The Search for Extraterrestrial Intelligence (SETI) is restricted to stars whose masses are comparable to the Sun. Explain. See pp. 747-748. H 2. In the Urey-Miller experiment, the simplest of the amino acids, glycine (C2H5O2N) has been made by running an electrical discharge through a gaseous mixture of ammonia (NH3), methane (CH4), carbon dioxide (CO2) and water (H2O). See p. 741. Glycine has also been found in the interstellar medium, and in the Murcheson meteorite. Is it possible that life’s origin is the result of amino acids from in space? Not so far as we know! Amino acids have structures that can be either “right handed (D)” or “left handed (L)”. Amino acids from space are very close to a 50-50 mixture of L and D amino acids. This is not the case for the amino acids in living systems, in which the L/D ratio is almost always very far from a 50-50 mixture. The only way to start life using amino acids from space is to dramatically change the L/D ratio, and we don’t know how this might have happened. The conclusion is that we cannot presently see a way for life to evolve from amino acids arriving from space. Write a paragraph in which you react to, or question, this conclusion.
H 1. On p. 699, the universe is depicted as the surface of an expanding balloon. The surface of a balloon is finite, and it has no edge, and no center. In this 2-dimensional model of the universe, you must imagine that all of space, and all stars and galaxies, are confined to the surface of the balloon. For this reason, the stars and galaxies must be thought of as having zero thickness, because a surface has no thickness, by definition. There is no space inside the balloon or outside of the balloon. The only space that exists is that which is represented by the surface. I call this the "Expanding Balloon Analogy" (EBA), and the EBA is the best I can do when I try to describe the properties of space. i.e. We think that 3-dimensional space really is finite, and that it has no edge and no center! Space is expanding, but it is not expanding into anything, because there is no “outside” to the 3-dimensional universe in the same way that there is no “outside” to the 2-dimensional surface of a balloon. Write a paragraph in which you react to, and/or question the EBA as an analogy for the expanding universe. H 2. The Cosmic Microwave Background is isotropic. What does that mean? H 3. The first stars were “pure” hydrogen-helium stars because these were the only elements made in the Big Bang.—i.e. Without nucleosynthesis, all stars and planets would be composed entirely of hydrogen and helium. Stars in Open Clusters (OC) contain all of the elements, but stars in Globular Clusters (GC) appear to be “pure” hydrogen-helium stars. Why do that OC stars contain all of the elements while GC stars are pure hydrogen-helium? Hint # 1: The interstellar medium is enriched by supernovae. See Sec. 21.5 on p. 561. Hint #2: Where are Open Clusters found in the Milky Way Galaxy? Hint # 3: Where are Globular Clusters found in the Milky Way Galaxy? H 4. The He/H ratio in the universe is less now than it was when the first atoms formed, and this ratio continues to decrease. Explain. H 5. Describe: a) The Solar System in terms of the number of planets, moons, asteroids and comets. b) The Milky Way Galaxy in terms of the number of stars. c) The visible universe in terms of the number of galaxies. See pp. 363-365, p. 616 and p. 697.
H 1. Explain why it is that the brightest Main Sequence stars in Open Clusters are much more massive than the brightest Main Sequence stars in Globular Clusters. See Fig. 20.17 on p. 532. For R4: See p. 546, especially Collapse of the Iron Core.
In R2: Identify the most abundant atoms in the interstellar gas. For R19: See p. 469 and p.169. In R1: Begin your answer with a collapsing protostar, and end at Main Sequence. See Table 19.1. In R1: You should discuss energy generation protostars, and explain why the collapse stops when it reaches Main Sequence. For R20: See p. 504 and "The Local Bubble" on p. 470.
H 1. Compare the composition of Jupiter to the composition of the Sun. See Ch. 11 and p. 393, 414. For R1: In your parallax explanation, you should: a) Describe the role of very distant "fixed stars". b) Explain why the "fixed stars" do not exhibit parallax shifts. c) Explain why there is a 6 month interval between parallax photos. H 2. Luminosity and surface temperature are used to plot a star’s position on an H-R diagram. a) Explain how luminosity is measured using the inverse square law on p. 441. b) Explain why it is that the only stars that can be plotted on an H-R diagram are those stars whose distances can be measured using parallax.
For P 1: Assume circular orbits for both Earth and Mercury, i.e. (orbit radius) = (semimajor axis) for each planet. See Table 3A in Appendix 3. For P 2: (The weight of a 150 kg astronaut on Earth) = mg = 1470 Newtons. Use Newton’s law of gravity (p.52). It’s a waste of time to plug values for r, m1, and m2 into this equation. Use a proportion, and remember that F varies inversely as the square of the center-to-center distance!
For R11 in Ch. 5: For this question, I want you to use the angular resolution equation on p. 116. Use the Keck Telescope (p. 115) at 550 nm for the optical telescope. For the radio telescope, use a frequency of 1 Ghz with the Very Long Baseline Interferometer (VLBI). See p. 128. For the frequency to wavelength conversion, see p. 71, and use the wave speed equation on p. 64. Assume that: (max. distance between VLBI telescopes) = (2/3 of Earth’s diameter). H 1 for Ch 6: The Solar System contains 9 planets, 58 moons, and thousands of asteroids within 40 AU of the Sun. The Oort Cloud of comets orbit the Sun at distances out to ~100,000 AU. The distance to the nearest star, Alpha Centauri, is 274,000 AU (1.33 pc). Compare the distance to Alpha Centauri to the diameter of the Sun. See the Appendices. Round your answer to 1 sig. fig. In regions where 1.33 pc is a typical distance between stars, the probability of collisions between stars is very small. Explain.
Sept. 3, 5 The Birth of Modern Science
Aug. 27, 29 Astronomy & the Universe