Measuring the Stars Chapter 10 Chapters 17, 19, 18 1
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Lecture-Tutorial on Parallax and the Parsec p 37 6) Consider two stars (C and D) that both exhibit parallax. If C appears to move back and forth by a greater amount than D, which do you think is actually closer to you? C. Star C D. Star D 5
9) If the parallax angle for Star A (p A ) is 1 arcsecond, what is the distance from the Sun to Star A? (Hint: Use parsec as your unit of distance.) 10) Is a parsec a unit of length or a unit of angle? It can t be both. 12) Place a second star Star B on the dotted line, farther from the Sun than Star A. Which star, the closer one (Star A) or the farther one (Star B), has the larger parallax angle? 6
1) Which of the following stars is closest to us? a. Procyon (parallax angle = 0.29 ) b. Ross 780 (parallax = 0.21 ) c. Regulus (parallax = 0.04 ) d. Sirius (parallax = 0.38 ) 7
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What do you do in a Lecture-Tutorial? Work with a partner (or group of 3)! Read the instructions and questions carefully. Discuss the concepts and your answers with one another. Take time to understand it now! Come to a consensus answer you all agree on. If you get stuck, or are not sure of your answer, ask another group. If you re still stuck, raise your hand, and I ll help. 9
5) The star Lee has an apparent magnitude of 0.1 and is located about 250 pc away from Earth. Which of the following is most likely the absolute magnitude for Lee? A. -6.9 B. 0.1 C. 7.1 10
Vega has an apparent magnitude of 0.03 and an absolute magnitude of 0.58. If it were moved twice as far from Earth as it is now, which of the following would occur? a) Apparent magnitude number would increase b) Apparent magnitude number would decrease c) Apparent magnitude number would stay the same d) Absolute magnitude number would increase e) Absolute magnitude number would decrease 11
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http://wwnorton.com/college/astronomy/under standing-our-universe/ 19
The Harvard Computers, 1913 20
If you analyze the light from a low density object (such as a cloud of interstellar gas), which type of spectrum do you see? a. Dark line absorption spectrum b. Bright line emission spectrum c. Continuous spectrum 21
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The two axes on the Hertzsprung- Russell (H-R) diagram can be a) luminosity and temperature. b) apparent magnitude and absolute magnitude. c) radius and main sequence. d) radius and luminosity. e) spectral type and temperature. 25
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Lecture-Tutorial book page 55: Luminosity, Temp, and Size 27
If you have two hot plates of the same temperature, which will cook the large pot of spaghetti first? a. The smaller hot plate. b. The bigger hot plate. c. Both will cook at the same rate since the temperature is the same. If two stars have the same temperature, but Star Jack is more luminous than Star Jill, which of the following is true? a. Jack is bigger than Jill b. Jill is bigger than Jack c. Jack and Jill are the same size d. There is no way to tell which star is bigger. 28
If two stars have the same size, but Star Alpha has a higher surface temperature than Star Beta, which of the following is true? a. Alpha is more luminous than Beta. b. Beta is more luminous than Alpha. c. Alpha and Beta have the same luminosity. d. There is no way to tell which star is more luminous. Lecture-Tutorial book page 55: Luminosity, Temp, and Size 29
Look at the HR diagram. Which star is larger, X or Y? a. X is larger b. Y is larger c. Same size d. No way to tell Look at the HR diagram. Which star is larger, Y or V? a. Y is larger b. V is larger c. Same size d. No way to tell 30
Suppose a star gets more luminous but does not change its temperature. What is happening? A. The star is contracting. B. The star is expanding C. The star is getting more massive. D. The star is changing its spectral type. AstroTour Stellar Spectrum Click here to launch this AstroTour (Requires an active Internet connection.) 31
AstroTour Atomic Energy Levels and the Bohr Model Click here to launch this AstroTour (Requires an active Internet connection.) AstroTour Atomic Energy Levels and Light Emission and Absorption Click here to launch this AstroTour (Requires an active Internet connection.) 32
AstroTour H-R Diagram Click here to launch this AstroTour (Requires an active Internet connection.) 33