MT2_with_answers - AST 101 Introduction to Astronomy Second...

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AST 101─ Introduction to Astronomy Second Midterm Exam (11/9/2007) Instructions A. Answer ALL questions on your Opscan, using a #2 pencil. B. Make sure to include your NAME and STUDENT ID . The computer identifies you by your student ID; do not forget to include it. C. Do NOT mark your date of birth. D. The exam is CLOSED BOOK . You should not use any books or notes. E. Time: 50 MINUTES . MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) What causes the radio pulses of a pulsar? A) The star's orbiting companion periodically eclipses the radio waves emitted by the main pulsar. B) The star undergoes periodic explosions of nuclear fusion that generate radio emission. C) As the star spins, beams of radio radiation sweep through space. If one of the beams crosses the earth, we observe a pulse. D) A black hole near the star absorbs energy and re - emits it as radio waves. E) The star vibrates. 2) Cluster ages can be determined from A) main sequence turnoff. B) spectroscopic binaries. C) pulsating variable stars. D) main sequence fitting. E) visual binaries. 3) What happens to the surface temperature and luminosity when a protostar radiatively contracts? A) Its surface temperature remains the same and its luminosity decreases. B) Its surface temperature and luminosity decrease. C) Its surface temperature decreases and its luminosity increases. D) Its surface temperature and luminosity increase. E) Its surface temperature and luminosity remain the same. 1
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AST 101─ Introduction to Astronomy 4) Why does a star grow larger after it exhausts its core hydrogen? A) Hydrogen fusion in a shell outside the core generates enough thermal pressure to push the upper layers outward. B) The internal radiation generated by the hydrogen fusion in the core has heated the outer layers enough that they can expand after the star is no longer fusing hydrogen. C) Helium fusion in the core generates enough thermal pressure to push the upper layers outward. D) Helium fusion in a shell outside the core generates enough thermal pressure to push the upper layers outward. E) The outer layers of the star are no longer gravitationally attracted to the core. 5) What happens after a helium flash ? A) The star breaks apart in a violent explosion. B) The core suddenly contracts. C) The core quickly heats up and expands. D) The star starts to fuse helium in a shell outside the core. E) The core stops fusing helium. 6) Suppose that you measure the parallax angle for a particular star to be 0.5 arcsecond. The distance to this star is A) 2 parsecs. B) 0.5 parsec. C) 5 parsecs. D) 0.5 light - year. E) 5 light - years. 7) Which of the following is the most common type of main - sequence star? A) an O star
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This note was uploaded on 03/03/2011 for the course RSM 100 taught by Professor Oesch during the Spring '08 term at University of Toronto- Toronto.

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MT2_with_answers - AST 101 Introduction to Astronomy Second...

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