Measuring Galaxies Test Bank Docx Ch14 - Understanding Our Universe 3e Complete Test Bank by Stacy Palen. DOCX document preview.
Chapter 14: Measuring Galaxies
LEARNING OBJECTIVES
14.1 Galaxies Come in Many Sizes and Shapes
14.1a Understand the meaning of homogeneous and isotropic.
14.1b Compare and contrast spiral and elliptical galaxies in terms of their shapes and structures.
14.1c Understand how stellar orbits determine the morphology (shape) of a galaxy or its components.
14.1d Compare and contrast spiral and elliptical galaxies in terms of their gas and dust content, color, luminosity, stellar populations, and mass.
14.2 There Are Many Ways to Measure Distance
14.2a Summarize the evidence for spiral arms being regions of star formation.
14.2b Recall how Shapley determined the size of the Milky Way Galaxy and our place in it.
14.2c Describe the distance ladder.
14.3 We Live in an Expanding Universe
14.3a Describe how we measure distances to faraway galaxies.
14.3b Explain why the Hubble redshift-distance relationship implies that we live in an expanding universe.
14.3c Explain why we are not at the center of an expanding universe.
14.4 A Supermassive Black Hole Exists at the Heart of Most Galaxies
14.4a Understand how the period of variability of an object places limits on its physical size.
14.4b Summarize the observational evidence for galaxies containing supermassive black holes at their centers, as black holes emit no observable radiation of their own.
14.4c Explain how an AGN differs from the nucleus of an ordinary galaxy.
Working It Out 14.1
Working It Out 14.1a Use Doppler shifts and the Hubble redshift-distance law to relate recessional velocity, redshift, and distance.
Chapter 14: Measuring Galaxies
MULTIPLE CHOICE
1. The following figure indicates a possible picture of a theoretical universe with two separate observers within it. Which of the following statements describes this universe?
a. This universe is homogeneous but not isotropic.
b. This universe is isotropic but not homogeneous.
c. This universe is both homogeneous and isotropic.
d. This universe is neither homogeneous nor isotropic.
2. What do astronomers mean when they say that the universe is homogeneous?
a. All stars in all galaxies have planetary systems just like ours.
b. The universe appears the same no matter where you look.
c. Galaxies are generally distributed similarly throughout the universe.
d. Generally there is little difference between conditions on Earth, in the Sun, or in outer space.
3. What do astronomers mean when they say that the universe is isotropic?
a. All stars in all galaxies have planetary systems just like ours.
b. The universe appears the same no matter where you look.
c. Galaxies are generally distributed similarly throughout the universe.
d. Generally there is little difference between conditions on Earth, in the Sun, or in outer space.
4. The following figure indicates a possible picture of a theoretical universe with two separate observers within it. Which of the following statements describes this universe?
a. This universe is homogeneous but not isotropic.
b. This universe is isotropic but not homogeneous.
c. This universe is both homogeneous and isotropic.
d. This universe is neither homogeneous nor isotropic.
5. The following figure indicates a possible picture of a theoretical universe with two separate observers within it. Which of the following statements describes this universe?
a. This universe is homogeneous but not isotropic.
b. This universe is isotropic but not homogeneous.
c. This universe is both homogeneous and isotropic.
d. This universe is neither homogeneous nor isotropic.
6. Which of the following galaxies can be found with a barlike structure in them?
a. spiral c. irregular
b. elliptical d. All are valid choices.
7. A galaxy that is classified as Sc would have
a. tightly wound spiral arms and a large central bulge.
b. loosely wound spiral arms and a large central bulge.
c. tightly wound spiral arms and a small central bulge.
d. loosely wound spiral arms and a small central bulge.
8. A galaxy that has a disk shape but no spiral arms is classified as
a. E0. c. Sa.
b. S0. d. SBa.
9. Examine the galaxies in the following images. What prominent feature distinguishes the bottom row from the top row?
a. bulge size c. bar-shaped bulges
b. disk size d. brightness
10. Which galaxy type is characterized by a spherical shape and a lack of spiral arms or disk structure?
a. E0 c. Sa
b. S0 d. SBa
11. Stars in this type of galaxy or region travel in the same direction around the galaxy’s center
a. the arms of spiral galaxies. c. elliptical galaxies.
b. the bulges of spiral galaxies. d. irregular galaxies.
12. Examine the galaxies in the following images. Which galaxy resembles an E7 type the closest?
a. c.
b. d.
13. If we lived in a galaxy 1 billion light-years from our own, what would we see?
a. a universe 1 billion years younger than ours
b. a universe 1 billion years older than ours
c. much the same universe we see today
d. Nothing—there are no galaxies 1 billion light-years away from us.
14. Besides shape, what characteristic clearly separates elliptical galaxies from spiral galaxies?
a. size c. age
b. mass d. color
15. In the Great Debate of 1920, Curtis and Shapley argued about whether spiral and elliptical nebulae were inside or outside of the Milky Way. These objects are now known as
a. dark matter. c. galaxies.
b. supermassive black holes. d. globular clusters.
16. Astronomers have known that galaxies are separate entities outside of our own for roughly the past
a. 30 years. c. 150 years.
b. 100 years. d. 300 years.
17. Which of the following is associated with the arms of a spiral galaxy?
a. density waves c. lack of dust lanes
b. lack of stellar formation d. random stellar orbits
18. Harlow Shapley determined the size of our Milky Way Galaxy and our place in it by studying __________ in __________?
a. Cepheids; open clusters c. RR Lyrae stars; globular clusters
b. Cepheids; globular clusters d. RR Lyrae stars; open clusters
19. Correctly rank the distance ladder in terms of techniques used to measure distances from the closest to the most distant objects.
a. radar, parallax, spectroscopic parallax, Cepheids, Type Ia supernovae
b. parallax, radar, spectroscopic parallax, Cepheids, Type Ia supernovae
c. Type Ia supernovae, parallax, Cepheids, spectroscopic parallax, radar
d. Cepheids, Type Ia supernovae, parallax, spectroscopic parallax, radar
20. Which technique measures distances by comparing the apparent brightness with the object’s luminosity?
a. radar c. spectroscopic parallax
b. parallax d. All are valid choices.
21. Which technique is only useful for measuring distances within the solar system?
a. radar c. spectroscopic parallax
b. cepheids d. All are valid choices.
22. Which technique can measure distances to the edges of the observable universe?
a. radar c. spectroscopic parallax
b. Cepheids d. Type Ia supernovae
23. Which technique is only useful for measuring distances to nearby stars?
a. radar c. spectroscopic parallax
b. Cepheids d. Type Ia supernovae
24. To be a standard candle, an object must have a known
a. lifetime. c. luminosity.
b. brightness. d. distance.
25. Why can Type Ia supernovae be used to determine a galaxy’s distance?
a. Type Ia supernovae occur only in very luminous galaxies.
b. Type Ia supernova have approximately the same luminosity.
c. Type Ia supernovae have approximately the same size.
d. A Type Ia supernova occurs in a typical galaxy about once every 100 years.
26. Galaxies move away from us in all directions because
a. the force of gravity strengthens with distance.
b. the force of gravity weakens with distance.
c. space is expanding.
d. our galaxy has expelled all other galaxies.
27. According to Hubble’s law, as the distance of a galaxy __________, its __________ increases.
a. increases; luminosity c. decreases; luminosity
b. increases; recessional velocity d. decreases; recessional velocity
28. The spectra of distant galaxies tell us that
a. most galaxies appear to be moving away from us.
b. their light comes predominantly from objects other than stars.
c. most galaxies contain clouds of gas that are absorbing random wavelengths.
d. galaxies in the past rotated at a faster rate than they do today.
29. Why are some galaxies’ spectra blueshifted rather than redshifted?
a. Some distant galaxies are gravitationally lensed.
b. Some nearby galaxies are attracted to us because of the mass of the Milky Way.
c. Some nearby galaxies have vigorous star formation and are much bluer than others.
d. Some distant galaxies have an AGN at their centers.
30. Astronomers use galactic redshift as a measure of
a. gravity. c. velocity.
b. distance. d. mass.
31. What did Edwin Hubble study in the Andromeda Galaxy that proved it was an individual galaxy and not part of our own Milky Way?
a. Cepheid stars c. globular clusters
b. Type Ia supernovae d. red giant stars
32. The Hubble constant, H0, represents the
a. rate of expansion of the universe.
b. speed at which galaxies are moving away from us.
c. time it takes a galaxy to move twice as far away from us.
d. size of the universe.
33. Which is true about the Hubble constant, H0?
a. It describes the rate of expansion of the universe.
b. It is the slope in a plot of recession velocity versus distance for distant galaxies.
c. It is about 70 km/s/Mpc.
d. All choices are valid.
34. Why is the current determination of the Hubble constant (H0) better than what Edwin Hubble determined?
a. It includes more accurate velocity measurements made with modern equipment.
b. It includes a larger sample of galaxies over much greater distances.
c. It includes more accurate distances measured with modern methods not available to Hubble.
d. All choices are valid.
35. The following figure shows the spectrum of a star (top) whose motion compared with our star is nearly stationary within the Milky Way Galaxy. The galaxy spectrum (bottom) indicates that the galaxy is
a. moving toward us. c. stationary.
b. moving away from us. d. There is not enough information.
36. If you found a galaxy with a hydrogen emission line, normally found at 656.3 nanometers (nm), with a measured wavelength of 756.3 nm, what would be the galaxy’s redshift, z?
a. 0.01 c. 0.10
b. 0.05 d. 0.15
37. If you found a galaxy with a hydrogen line, normally found at 122 nm, with a measured wavelength of 125 nm, what would be the galaxy’s redshift?
a. 0.02 c. 1.02
b. 0.98 d. 3.00
38. If a galaxy has a recessional velocity of 910 kilometers per second (km/s), what is its distance if the Hubble constant is 70 km/s/megaparsec (Mpc)?
a. 0.007 Mpc c. 840 Mpc
b. 13 Mpc d. 63,700 Mpc
39. If the distance of a galaxy is 100 Mpc, what is its recessional velocity if the Hubble constant is 70km/s/Mpc?
a. 0.70 km/s c. 1,000 km/s
b. 1.40 km/s d. 7,000 km/s
40. If the distance of a galaxy at a redshift z 
0.5 is 1,800 Mpc, what is H0?
a. 3,600 km/s/Mpc c. 83 km/s/Mpc
b. 0.0003 km/s/Mpc d. 900 km/s/Mpc
41. If you measured the distances and recessional velocities for a sample of galaxies and plotted the data to get the following figure, what value would you derive for the Hubble constant?
a. 10 km/s/mega-light-year (Mly) c. 45 km/s/Mly
b. 22 km/s/Mly d. 100 km/s/Mly
42. If you found a galaxy with a hydrogen emission line, normally found at 656.3 nm, with a measured wavelength of 756.3 nm, what would the galaxy’s recessional velocity be if the Hubble constant is 72 km/s/Mpc?
a. 39,700 km/s c. 47,000 km/s
b. 45,700 km/s d. 54,500 km/s
43. If the spectrum of a distant galaxy is observed to have a calcium K absorption line that occurs at a wavelength of 500.4 nm, what is this galaxy’s distance if the rest wavelength of this absorption line is 393.4 nm? Assume a Hubble constant of 72 km/s/Mpc.
a. 950 Mpc c. 2,300 Mpc
b. 1,800 Mpc d. 1,130 Mpc
44. What is a quasar?
a. an active galactic nucleus (AGN) powered by a supermassive black hole
b. a star that only emits radio waves
c. a star made up of quarks
d. a galaxy that has its light affected by a gravitational lens
45. What is the size of the region responsible for powering an AGN?
a. atomic size c. solar system size
b. stellar size d. galaxy size
46. What accounts for the different types of observed AGNs?
a. galaxy’s age
b. galaxy’s distance
c. galaxy’s mass
d. orientation of the galaxy to our line of sight
47. About how massive is the supermassive black hole at the center of the Milky Way Galaxy?
a. 4 solar masses c. 40,000 solar masses
b. 400 solar masses d. 4 million solar masses
48. How did astronomers determine the mass of the supermassive black hole at the center of the Milky Way Galaxy?
a. direct observations of stars orbiting the black hole.
b. brightness variability of Sagittarius A*
c. measurements of gamma-ray bubbles.
d. Its mass is still completely unknown.
49. Examine the following image. The polar gamma-ray bubbles and jets emanating from the center of the Milky Way Galaxy are likely evidence of
a. past episodes of infalling material into the supermassive black hole.
b. current stellar formation around the supermassive black hole.
c. ongoing outbursts from around the supermassive black hole.
d. radiation escaping from inside the supermassive black hole.
50. Examine the following image. The tilted gamma-ray jets emanating from the center of the Milky Way Galaxy are likely evidence that
a. they are not associated with the supermassive black hole.
b. the accretion disk around the supermassive black hole is also tilted.
c. dark matter alters the trajectory of the jets.
d. the expansion of the universe alters the trajectory of the jets.
1. Describe the two assumptions regarding the universe that the cosmological principle makes.
2. What are the three main types of galaxies, and how do they differ in appearance?
3. Explain the differences between a galaxies classified as type E0 and E7.
4. What are the two major characteristic differences between galaxies classified as type Sa, Sb, and Sc?
5. What is the likely reason behind the irregularity of the Irr class of galaxies?
6. Describe the S0 class of galaxies. Compare and contrast their characteristics with other types.
7. What were the positions taken by Heber Curtis and Harlow Shapley in their “Great Debate,” and how were both of them partially correct?
8. Label the following regions, objects, and lengths in the following figure of the Milky Way Galaxy: galactic halo, Magellanic Clouds, galactic disk, globular clusters, galactic bulge, Sun, 300,000 light-years, 100,000 light-years, and 27,000 light-years.
9. Name three “rungs” in the distance ladder that let us estimate the value of H0.
10. Examine the following figure. Describe why the distance ladder is so important to the field of cosmology.
11. Describe how Harlow Shapley made a three-dimensional map of the Milky Way Galaxy and how he determined our location in it.
12. Describe the characteristics of a globular cluster.
13. How did Edwin Hubble definitively prove that “spiral nebulae” were individual galaxies that were separate from the Milky Way?
14. Does Hubble’s law imply that our galaxy is sitting at the center of the universe? Explain.
15. The spectrum of a galaxy is observed to have a hydrogen emission line, normally found at
656.3 nm, with a measured wavelength of 928.7 nm. What is its redshift?
16. The spectrum of a galaxy is observed to have a hydrogen emission line, normally found at 656.3 nm, with a measured wavelength of 856.3 nm. What is its distance if the Hubble constant is 70 km/s/Mpc?
17. Compare and contrast X-ray binary stars to AGNs.
18. Compare and contrast an AGN to a normal galaxy.
19. Describe how the Milky Way Galaxy’s supermassive black hole was found to reside in the Sagittarius A* region and how its mass was determined.
20. Explain the connection between quasars and AGNs and their source of power.