Fall 2000 ASTR 1120-001 Review for Quiz 2

The quiz will contain 10 multiple-choice questions, and will be 10 minutes long. The intention is that all material on the quiz (saving matters of logic and common sense) is referred to somewhere here.

  1. Absolute Temperature. Review the worksheet on Temperature. What is absolute temperature? What is the conversion factor between energy and Kelvin? What is absolute zero? When can an object be described by a temperature? What is thermodynamic equilibrium? What is the spectrum of an object in thermodynamic equilibrium called? What is Wien's Law? What is the Stefan-Boltzmann Law?

  2. Gravity. If a gravitating system loses energy, does it cool down (decrease temperature) or heat up (increase temperature)? Explain. Give one or more examples where this happens in astronomy.

  3. Plasma. What is a plasma? Under what conditions does matter become a plasma?

  4. Eddington. What profound new idea did Eddington have about the condition of matter inside the Sun that revolutionized our concept of the Sun? How did Eddington estimate the temperature at the center of the Sun? For a description of his ideas in his own words, read Eddington's 1920 Address.

  5. Hydrostatic Equilibrium. Bennett calls this `gravitational equilibrium'. What is hydrostatic equilibrium? Is the Sun in hydrostatic equilibrium? Explain.

  6. Solar Energy. What is the source of the Sun's energy? Back at the beginning of the 20th century, a leading theory was Kelvin's suggestion that the Sun was powered by its own gravitational contraction? What was wrong with that theory? Has the Sun ever been powered by gravitational contraction?

  7. Nuclear Fusion. Give an account of the fusion of hydrogen to helium in the Sun. Where does the energy come from?

  8. Bomb. Why doesn't the Sun explode like a nuclear bomb? What are the 2 essential ingredients of a bomb?

  9. Doppler effect. What is the Doppler effect? What is a redshift? Blueshift?

  10. Helioseismology. What is helioseismology? What do astronomers learn from helioseismology? To find out more, visit the superb Helio- and Asteroseismology site at the Institute for Physics and Astronomy, Aarhus University, Denmark.

  11. Solar Spectrum. Describe the Sun's spectrum. What are Fraunhofer (1814) lines? Explain why the Sun's spectrum looks the way it does. What is it possible to learn from the spectrum of the Sun?

  12. Stellar Spectra. What are Henry Draper, Annie Jump Cannon, and Cecilia Payne-Gaposchkin famous for? What is spectral type? What has temperature got to do with spectral type? What is the sequence of spectral types?

  13. Ha in stars. In what spectral type of star is the Ha line strongest? Is the line in absorption or emission? Draw an atomic energy level diagram of H showing the Ha, Hb, Hg ... lines. Sketch a graph showing how the strength of the Ha line varies with temperature. Explain physically why the Ha line varies with temperature the way it does.