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Dec 6, 2023





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Name Peoplesoft # Exam 2 - Version D (Blue) Astronomy 0089: Stars, Galaxies, and the Cosmos 1. Fill in your Name and Peoplesoft ID number on this test (above) and on the scantron form be sure to bubble in the Peoplesoft ID. 2. Please fill in your name and SIGNATURE on your answer sheet. Your signature affirms that you will not share the contents of this exam with anyone outside class. 2. Be sure to answer the last two questions correctly. Getting these questions right will ensure your exam is graded properly. 3. ALWAYS SELECT THE BEST ANSWER. There is only one best answer for each question. Read each question carefully before answering. 4. Be sure to answer all questions; no points are deducted for guessing. 5. If you have any questions, please raise your hand and ask them when we come to you. 6. Return this exam booklet along with the scoresheet when you are done with the exam
This exam has extra proportionality questions at the end to give you plenty of opportunity to practice. I expect our actual exam to have roughly 30-35 questions in total, of which 4-5 may apply proportionalities directly. 1. Suppose you find a binary star consisting of Stars A and B orbiting each other with a semimajor axis of 1 AU. Each star has a mass half as large as the Sun. What would their orbital period be? A) A and B would each have different orbital periods B) Between 10 and 100 years C) 1 year D) Between 1 and 10 years E) Less than one year 2. Two stars, Thuban and SUPERBLINK 23261+1600, each have a surface temperature of 10000 K. Which star has a greater luminosity? A) The luminosities of the two stars must be the same B) Insufficient information has been provided to determine the answer C) Thuban D) SUPERBLINK 23261+1600 3. During a total solar eclipse, you can see the low-density outer atmosphere of the Sun, which you normally cannot see from Earth. What is this atmosphere called? A) Radiative zone B) Penumbra C) Corona D) Photosphere E) Core 4. Mira is a star with about the same mass as the Sun. What color is it?
A) Yellow B) You can't answer this question with the information given C) Blue D) Red E) Green 5. How can we measure the masses of stars? A) You would need to go there and use a really big scale B) If you know the star's color, you can use that to calculate its mass- all stars of the same color have the same mass C) By observing the orbits of binary stars D) If you know the star's luminosity, you can always use that to calculate its mass E) c and d 6. The stars Canopus and Alpha Centauri have about the same apparent brightness. What can we say about their luminosities? A) You would have to know their distances to know which has a higher luminosity B) You would have to know if they are both ideal thermal emitters to know which has a higher luminosity C) They must be about the same D) You would have to know their colors to know which has a higher luminosity E) You would have to know their radii to know which has a higher luminosity 7. How does the Sun produce energy? A) By fission of uranium into lighter elements B) Energy is being produced in different ways in different layers of the Sun C) By fusion of hydrogen into helium D) By fusion of helium into carbon E) By chemical reactions of hydrogen and oxygen into water 8. Saturn is 10 AU from the Sun. How bright would the Sun appear from Saturn, compared to how it appears on Earth? A) It would be 10 times as bright B) It would be 1/1000 as bright C) It would have the same brightness, as its luminosity is the same D) It would be 1/10 as bright E) It would be 1/100 as bright 9. How is energy transferred through the radiative zone of the Sun?
A) The Sun's energy is generated in the radiative zone and is transferred through other zones B) It is transferred by blobs of hotter material rising and cooler material sinking C) It is transferred by light traveling outward D) It is transferred by direct thermal contact between material, like hot coffee heating up the mug it is in 10. Why do stars have different colors? A) Hotter stars appear bluer and cooler stars appear redder B) Hotter stars appear redder and cooler stars appear bluer C) Higher-mass stars appear redder and lower-mass stars appear bluer D) Higher-luminosity stars appear bluer and lower-luminosity stars appear redder E) Higher-mass stars appear bluer and lower-mass stars appear redder 11. Where is energy being generated in the Sun? A) Radiative zone B) Convective zone C) The Sun generates energy throughout its interior D) Photosphere E) Core 12. Betelgeuse and Lalande 21185 appear exactly the same color, but Betelgeuse has a much higher luminosity than Lalande 21185. What can we conclude from this? A) Betelgeuse has a lower surface temperature than Lalande 21185 B) Betelgeuse has a smaller radius than Lalande 21185 C) Betelgeuse has a higher surface temperature than Lalande 21185 D) Betelgeuse has a larger radius than Lalande 21185 E) Betelgeuse has a larger mass than Lalande 21185 13. What do we mean when we say that the Sun is in hydrostatic equilibrium? A) The force of pressure from within the Sun is in balance with the force of gravity, so the Sun stays about the same size B) The force of gravity is in balance with the static electricity generated by the Sun's magnetic field, so the Sun stays about the same size C) The temperature of the Sun is the same throughout its interior D) The Sun is at the center of the solar system and is not moving E) Plumes of water rise and sink in the Sun's interior, and transport energy from the core to the surface 14. Which of the following is a type of observation that has allowed us to learn about the interior structure of the Sun?
A) Observations of the orbits of the planets B) Observations of oscillations of the Sun (helioseismology) C) Observations from space probes that were dropped into the Sun D) Measurements of the spectrum of sunlight 15. How can we determine the surface temperature of a distant star? A) From its apparent brightness B) From the orbit of a planet or binary companion around it C) We can't, we would need to go there with a thermometer to find out D) From its color E) From its luminosity 16. The star Adhara is a Main Sequence star with a mass roughly 10 times as large as the mass of the Sun. How should its Main Sequence lifetime compare to that of the Sun? A) Adhara will be on the Main Sequence about 1/1000 (one one-thousandth) as long as the Sun B) Adhara will be on the Main Sequence about the same amount of time as the Sun C) Adhara will be on the Main Sequence about 1/10 (one tenth) times as long as the Sun D) Adhara will be on the Main Sequence about 1/10,000 (one ten-thousandth) times as long as the Sun E) Adhara will be on the Main Sequence about 1/100 (one one-hundredth) times as long as the Sun 17. What force prevents white dwarfs from collapsing? A) Neutron degeneracy pressure B) Electron degeneracy pressure C) Electrical repulsion between negatively charged electrons D) Radiation pressure E) Centrifugal force 18. As the Sun evolves off the Main Sequence, it will lose some of its mass due to increased solar wind. Based on Newton’s version of Kepler’s Third Law, what will happen to the length of an Earth year after this happens as a result of this change in mass, assuming the semimajor axis of the Earth’s orbit remains unchanged? A) All of the planets will be vaporized by the explosion that will happen when the Sun leaves the Main Sequence, so Earth will not have a year B) It will be longer C) It will stay the same D) It will be shorter
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