# 5. A particular star has an angle of parallax of 0.2 arcsecond. What is the distance to this star? A) 50 pc B) 2 pc C) 5 pc D) 0.

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1 Name: Date: 1. How far away is the nearest star beyond the Sun, in parsecs? A) between 1 and 2 pc B) about 12 pc C) about 4 pc D) between 1/2 and 1 pc 2. Parallax of a nearby star is used to estimate its A) surface temperature. B) distance from Earth. C) apparent magnitude. D) physical size or diameter. 3. Stellar parallax appears because A) Earth rotates about its own axis. B) stars move in space. C) stars have finite size (i.e., they are not really just points of light). D) Earth moves in space. 4. What is the relationship between stellar parallax (p) measured in seconds of arc and distance (d) measured in parsecs? A) d = 1/p 2 B) d = 1/p C) d = p D) d = p 2 5. A particular star has an angle of parallax of 0.2 arcsecond. What is the distance to this star? A) 50 pc B) 2 pc C) 5 pc D) 0.2 pc 6. A particular star is 20 pc away from Earth. What is the stellar parallax for this star? A) 6 arcsec B) 20 arcsec C) 0.02 arcsec D) 0.05 arcsec Page 1

2 7. A star of apparent magnitude +1 appears than a star of apparent magnitude +2. A) either brighter or fainter, depending on the distance to the stars B) farther away C) brighter D) fainter 8. A star of apparent magnitude 2 appears than a star of apparent magnitude 3. A) fainter B) brighter C) farther away D) either brighter or fainter, depending on the distance to the stars 9. A star's absolute magnitude and its apparent magnitude have the same numerical value. How far is this star from Earth? A) It is not possible for a star to have the same absolute and apparent magnitudes. B) The star would have to be an infinite distance away. C) 10 ly D) 10 pc 10. Two stars whose apparent magnitudes differ from each other by five magnitudes have a ratio of brightnesses of A) 25. B) 10. C) 100. D) Sirius, visually the brightest star in our night sky, has an apparent magnitude of about 1.5 while the Andromeda Galaxy has an apparent magnitude of about What is the ratio of their brightnesses, as seen by Earthbound observers? A) The Andromeda Galaxy is 100 times brighter than Sirius. B) The Andromeda Galaxy is 2 times fainter than Sirius. C) The Andromeda Galaxy is 5 times brighter than Sirius. D) The Andromeda Galaxy is 100 times fainter than Sirius. 12. Luminosity is measured in A) watts. B) watts per second. C) watts per square meter. D) parsecs. Page 2

3 13. What is the fundamental difference between absolute and apparent magnitude of a star? A) The difference is +5 since absolute and apparent magnitude differ by this value by definition. B) Apparent magnitude depends on the star's temperature, whereas absolute magnitude is independent of temperature. C) Apparent magnitude depends on the size of the star, whereas absolute magnitude is independent of this parameter. D) Absolute magnitude is an intrinsic property of the star, whereas apparent magnitude depends on its distance from Earth. 14. Spectral types of stars (e.g., O, B, A, F, G, K, and M) uniquely define their A) sizes or radii. B) absolute magnitudes. C) luminosities. D) surface temperatures. 15. Which of the following sequences of stellar spectral classifications is in the correct order of increasing temperature? A) K, M, G, F, A, B, O B) A, B, F, G, K, M, O C) M, K, G, F, A, B, O D) O, B, A, F, G, K, M 16. Which of the following four spectral classifications signifies the coolest stellar surface temperature? A) B B) K C) G D) A 17. The Hertzsprung-Russell diagram is a plot of A) apparent brightness against intrinsic brightness of a group of stars. B) apparent brightness against distance for stars near the Sun. C) luminosity against mass of a group of stars. D) absolute magnitude (or intrinsic brightness) against temperature of a group of stars. 18. What are the two physical parameters of stars that are plotted in the Hertzsprung-Russell diagram? A) mass and surface temperature B) luminosity and mass C) radius and mass D) luminosity and surface temperature Page 3

4 19. As you move upward and to the left on the H-R diagram the stars become A) cooler and redder. B) hotter and redder. C) cooler and whiter. D) hotter and whiter. 20. What fraction of the stars surrounding the Sun are main-sequence stars? A) almost all, about 90% B) There are no main-sequence stars close to the Sun. C) roughly half, about 55% D) very few, about 20% 21. What is spectroscopic parallax? A) apparent change in position of the absorption lines in a star's spectrum due to the Doppler shift caused by Earth's motion around the Sun B) apparent change in position of a nearby star compared with distant background stars due to the motion of Earth around the Sun C) change in position of the absorption lines in a star's spectrum due to the Doppler shift caused by the star's motion around the center of mass in a binary star system D) distance to a star measured using the spectral luminosity class of the star and the inverse square law 22. How do astronomers measure the masses of stars? A) by observing the star's brightness at different wavelengths (colors) B) by observing the motion of two stars in a binary star system C) by measuring the star's brightness, temperature, and distance D) by measuring the star's brightness and obtaining its radius using the H-R diagram 23. A particular star in a binary star system orbits the other in an elliptical orbit with a semimajor axis of 3 AU and a period of 5 years. What is the sum of the masses of the two stars in the system? A) 0.9 B) 1.1 C) 13.9 D) Which sentence describes the relationship between mass and luminosity of stars on the main sequence? A) The luminosity of stars increases with mass up to a peak around 1 solar mass, then decreases as the mass continues to increase. B) Luminosity is independent of the stellar mass. C) The larger the stellar mass, the larger is the luminosity. D) The greater the stellar mass, the less is the luminosity. Page 4

5 Answer Key 1. A 2. B 3. D 4. B 5. C 6. D 7. C 8. A 9. D 10. C 11. D 12. B 13. D 14. D 15. C 16. B 17. D 18. D 19. D 20. A 21. D 22. B 23. B 24. C Page 5

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