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Astronomy Review for Chapter 79 Test You may bring in a 5” x 7” formulas note card with any problems worked on it and a separate note card (same size) with any other information you like that is relevant for the test. Textbook use is not allowed. What to study* • The Universe: “Secrets of the Sun” video notes • RedShift labs: “Star Colors”, “Star Brightness”, “H-R Diagram” – especially study the conclusions and summary tables in each lab. • Bad Astronomy article – “Star Light, Star White” • Chapter 7-9 Notes worksheets • Chapter 7-9 Powerpoint notes *Solutions to these documents can be found at rhsweb.org/assignments/Nash/Astronomy/ Some practice problems 1. The temperature of a gas is a measure of the a. total amount of internal energy in the gas. b. amount of heat that flows out of the gas. c. total number of atoms in the gas. d. density of the gas. e. average motion of its atoms. 2. The wavelength of maximum intensity that is emitted by a black body is a. proportional to temperature. b. inversely proportional to temperature. c. proportional to temperature to the fourth power. d. inversely proportional to temperature to the fourth power. e. Both a and c above. 3. Of the following, which color represents the lowest surface temperature star? a. Yellow. c. Orange. b. Blue. d. Red. e. White. 4. The amount of electromagnetic energy radiated from every square meter of the surface of a blackbody each second is a. proportional to temperature to the second power. b. inversely proportional to temperature. c. proportional to temperature to the fourth power. d. inversely proportional to temperature to the fourth power. e. Both a and c above. 5. The B - V color index of a star indicates its a. density. d. chemical composition. b. total mass. e. surface temperature. c. radius. 6. What conditions produce a dark (absorption line) spectrum? a. A hot solid, liquid, or high-density gas. b. A hot low-density gas. c. Light from a continuous spectrum source passing through a cooler low-density gas. d. Both a and b above. e. All of the above. 7. Of the following spectral types, which one represents a star with the highest surface temperature? a. A b. B c. F d. K e. G 8. You research the star Sirius and find that its spectral lines are blue shifted. What does this tell you about Sirius? a. Its surface temperature is higher than that of the Sun. b. It has a transverse velocity that is away from us. c. It has a transverse velocity that is toward us. d. It has a radial velocity that is away from us. e. It has a radial velocity that is toward us. 9. Which layer of the Sun's atmosphere contains the cooler low-density gas responsible for absorption lines in the Sun's spectrum? a. The photosphere. d. The solar wind. b. The chromosphere. e. All of the above. c. The corona. 10. Which of the following is true about granules and supergranules? a. They are both about the same size. b. Granules and supergranules each fade in about 10 to 20 minutes. c. They are both due to convection cells in layers below. d. Both a and c above. e. Both b and c above. 11. What are the general trends in temperature and density from the photosphere to the chromosphere to the corona? a. The temperature increases and density decreases. b. The temperature increases and density increases. c. The temperature decreases and density decreases. d. The temperature decreases and density increases. e. The temperature and density remain constant. 12. What heats the chromosphere and corona to high temperatures? a. Long-wavelength electromagnetic radiation emitted by layers below. b. Visible light emitted by layers below. c. Short-wavelength electromagnetic radiation emitted by layers below. d. Sungrazing comets, giving up their energy of motion as they vaporize in these two layers. e. Fluctuating magnetic fields from below that transport energy outward. 17. Why can smaller parallax angles be measured by telescopes in Earth orbit? a. Telescopes orbiting Earth are closer to the stars. b. Earth's atmosphere does not limit a telescope's resolving power. c. Earth's atmosphere does not limit a telescope's light gathering power. d. Earth's atmosphere does not limit a telescope's magnifying power. e. They can be connected to Earth-based telescopes to do interferometry. 13. What is the source of the Sun's changing magnetic field? a. The differential rotation of the Sun. b. Convection beneath the photosphere. c. The Sun's large iron core. d. Both a and b above. e. Both a and c above. 18. How can a cool star be more luminous than a hot star? a. It can be more luminous if it is larger. b. It can be more luminous if it is more dense. c. It can be more luminous if it is closer to Earth. d. It can be more luminous if it is farther from Earth. e. A cool star cannot be more luminous than a hot star. 14. How does the Sun maintain its energy output? a. Gravitational contraction. b. Fusion of hydrogen nuclei. c. The impact of small meteoroids. d. Coal burning in pure oxygen. e. Fission of Uranium 235. 15. What evidence do we have that sunspots are magnetic? a. The spectral lines of sunspots are split by the Zeeman Effect. b. Observations show that the north pole and south pole sunspots attract one another and move closer together over time. c. Observations at far ultraviolet show material arched above the Sun's surface from one sunspot to another. d. Both a and b above. e. Both a and c above. 16. Why does nuclear fusion require high temperatures? a. Protons have positive charge, and like charges repel one another. b. Two protons must get close enough together to overcome the Coulomb barrier. c. Two protons must get close enough for the strong force to bind them together. d. Both a and b above. e. All of the above. 19. A star has one-half the surface temperature of the Sun, and is four times larger than the Sun in radius. What is the star's luminosity? a. 64 solar luminosities. b. 16 solar luminosities. c. 4 solar luminosities. d. 2 solar luminosities. e. 1 solar luminosity. 20. In addition to the H-R diagram, what other information is needed to find the distance to a star whose parallax angle is not measurable? a. The star's spectral type. b. The star's luminosity class. c. The star's surface activity. d. Both a and b above. e. All of the above. Answers: 1e 2b 3d 4c 5e 6c 7b 8e 9a 10 c 11 a 12 e 13 d 14 b 15 e 16 e 17 b 18 a 19 e 20 d