mt2B - Astronomy 10 - Fall 2008 Midterm 2 November 13, 2008...

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Astronomy 10 - Fall 2008 Midterm 2 November 13, 2008 This test has 40 multiple-choice questions. You need Scantron form 882-E to take it. You are allowed to use a calculator and one page (double-sided) of written notes. All other materials and references should be put away. Note the list of equations and physical quantities attached to the back of this test. Be sure to write your full name , SID , and section number on your Scantron form. 1. THIS EXAM IS VERSION B. PLEASE ANSWER B TO QUESTION 1. 2. How do astronomers know that the Sun contains elements other than hydrogen and helium? (a) by observing sunspots (b) by observing solar flares (c) by observing oscillations of the solar surface (d) by observing absorption lines in the photosphere 3. When a star’s core becomes hot enough to ignite the triple α reaction, what is the primary element produced? (a) carbon (b) nitrogen (c) oxygen (d) iron 1
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4. In the triple α reaction, three helium nuclei fuse to create one carbon nucleus, with a net energy release of 7.275 MeV. How many reactions per second are necessary to sustain a stellar luminosity of 50 solar luminosities? ( Note: 1 MeV is equivalent to 1 . 602 × 10 - 6 erg.) (a) 1 . 64 × 10 40 (b) 1 . 44 × 10 41 (c) 1 . 74 × 10 41 (d) 1 . 54 × 10 42 5. Which of the following processes creates the Sun’s magnetic field? (a) hydrogen fusion near the center (b) convection and rotation in the solar interior (c) tidal forces from the orbiting planets (d) migration of sunspots across the solar surface 6. What is the Schwarzschild radius for a black hole with 100 times the mass of the Sun? (a) 3 × 10 4 cm (b) 3 × 10 5 cm (c) 3 × 10 6 cm (d) 3 × 10 7 cm 7. Consider a binary system so far away that you cannot resolve the separation of the individual stars. You know with certainty, however, that you are observing a binary, and that one star has twice the mass of the other. What piece of information, by itself, can tell you this? (a) the varying Doppler shifts of absorption lines (b) the observed parallax of the system (c) the observed color of the binary system (d) the apparent brightness of the system 2
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8. Which of the following statements about novae is true? (a) A white dwarf is destroyed during a nova. (b) A nova occurs in a binary system in which one component is a white dwarf. (c) A nova is caused by a sudden burst of nuclear fusion deep inside a white dwarf. (d) Our Sun will likely undergo at least one nova event after it becomes a white dwarf.
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mt2B - Astronomy 10 - Fall 2008 Midterm 2 November 13, 2008...

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