21st century astronomy the solar system fifth edition test bank chapter 19 by asmacandy

TEST BANK 21ST CENTURY ASTRONOMY THE SOLAR SYSTEM 5TH EDITION BY KAY IF You Want To Purchase A+ Work Then Click The Link Below , Instant Download

http://www.acehomework.net/?download=test-bank-21st-centuryastronomy-the-solar-system-5th-edition-by-kay If You Face Any Problem E- Mail Us At

whisperhills@gmail.com

Chapter 19: Galaxies LEARNING OBJECTIVES. Define the bold-faced vocabulary terms within the chapter. 19.1 Galaxies Come in Different Shapes and Sizes Evaluate how well Shapley and Curtis’s arguments about, and Hubble’s measurements of, the nature of galaxies conform to the established process of science laid out in this text. Multiple Choice: 1, 2, 4, 11, 14, 16 Short Answer: 5, 6 Illustrate the essential morphological (shape) characteristics of the Hubble types of galaxies. Multiple Choice: 3, 5, 6, 7, 8, 28 Short Answer: 3, 4 Show how stellar orbits determine the morphology of a galaxy or its components. Multiple Choice: 15 Short Answer: 1 Compare and contrast spiral and elliptical galaxies in terms of their gas and dust content, color,

luminosity, stellar populations, and mass. Multiple Choice: 9, 10, 12, 13, 17, 18 Short Answer: 2 19.2 Astronomers Use Several Methods to Find Distances to Galaxies Illustrate why measurements to increasingly distant objects require overlapping scales, each building on the previous “rung” of a “distance ladder.” Multiple Choice: 26 Short Answer: 8 Explain what is meant by “standard candle.” Multiple Choice: 19, 22, 23 Compare and contrast the observations needed to use the various distance indicators in this chapter, including Cepheids, Type Ia supernovae, and Hubble’s law. Multiple Choice: 20, 21, 24, 25, 27, 29 Short Answer: 9, 10, 11 19.3 Galaxies Are Mostly Dark Matter Explain how the amount of matter inferred from electromagnetic radiation can differ from that inferred from gravity. Multiple Choice: 43 Short Answer: 17, 18 Illustrate how flat rotation curves imply the need for dark matter. Multiple Choice: 42, 52 Short Answer: 16, 19 Summarize the observational evidence for dark matter in spiral and elliptical galaxies. Multiple Choice: 44, 48, 49, 50, 51, 53 Short Answer: 15 Compare and contrast the behavior of normal and dark matter. Multiple Choice: 45 Summarize the candidates for dark matter, and the observational evidence supporting or refuting each candidate. Multiple Choice: 46, 47 Short Answer: 14

19.4 Most Galaxies Have a Supermassive Black Hole at the Center Explain why astronomers initially believed quasars were stars. Multiple Choice: 59, 61, 68 Illustrate how the period of variability of an object places limits on its physical size. Multiple Choice: 63, 67, 69 Short Answer: 26, 30 Summarize the observational evidence for galaxies containing supermassive black holes at their centers, since black holes emit no observable radiation of their own. Multiple Choice: 70 Explain how an AGN differs from the nucleus of an ordinary galaxy. Multiple Choice: 57, 60, 62, 64, 66 Short Answer: 22, 23, 25, 28, 29 Illustrate the unified model of AGN and how different perspectives can lead to classification of the central engine as a different type of AGN. Multiple Choice: 58, 65 Short Answer: 21, 24, 27 Working It Out 19.1 Use the relationship between distance, luminosity, and brightness to calculate the distance to a standard candle. Short Answer: 7 Working It Out 19.2 Use Doppler shifts and the Hubble redshift-distance law to relate recessional velocity, redshift, and distance. Multiple Choice: 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41 Short Answer: 12, 13 Working It Out 19.3 Calculate the size, density, and accretion rate of a supermassive black hole. Multiple Choice: 54, 55, 56 Short Answer: 20

MULTIPLE CHOICE 1. What caused early astronomers to believe that our galaxy is only about 6,000 light-years Copyright ÂŠ 2015 Pearson Canada Inc.

iii

across? a. Telescopes were not powerful enough to observe stars farther away. b. Interstellar dust blocked visible light from stars farther away. c. Stars farther away could not be resolved as individual objects. d. Astronomers miscalculated the distances to stars, believing that the stars were 50 times closer than they actually were. e. Astronomers assumed all red stars were faint main- sequence stars, and they confused more luminous red giants with them. 2. In the Great Debate of 1920, Curtis and Shapley argued over whether or not a. the Big Bang occurred. b. the age of the universe was 14 billion years. c. the universe was contracting. d. life existed outside Earth. e. the spiral nebulae were located outside the Milky Way. 3. Which of the following Hubble images shows an edge-on disk galaxy?

4. Astronomers have known that galaxies are separate entities outside of our own for roughly the last a. 35 years. b. 60 years. c. 90 years. d. 150 years. e. 210 years. 5. The Hubble classification scheme for galaxies sorts them by their a. evolutionary state. b. mass. c. amount of dust. d. amount of dark matter. e. visual appearance. 6. What type of galaxy is shown in the figure below? a. a giant elliptical b. an ordinary spiral galaxy c. an irregular galaxy d. a barred spiral e. a dwarf elliptical 7. What type of galaxy is shown in the figure below? a. a giant elliptical b. a regular spiral galaxy c. an irregular galaxy d. a barred spiral e. a dwarf elliptical 8. In spiral galaxies, the size of the central bulge is correlated with the a. tightness of the spiral arms. b. luminosity of the galaxy. c. age of the galaxy. d. thickness of the disk. e. presence of an active nucleus. 9. Active star formation does not typically occur in elliptical galaxies because they a. rotate too fast. b. contain little molecular hydrogen. c. are too massive. d. are too far away.

e. usually contain active nuclei. 10. Elliptical galaxies appear red because they a. are moving away from us. b. contain mostly ionized hydrogen gas. c. contain mostly old stars. d. contain lots of dust. e. contain a mix of old and young stars. 11. One of the first philosophical speculations about the nature of spiral nebulae being “island universes” like our Milky Way, only much farther, came from a. Charles Messier. b. Immanuel Kant. c. Edwin Hubble. d. Harlow Shapley. e. Heber Curtis.

12. The dark features in the HST image in in the figure shown below indicate a. collections of cool stars. b. clumps of dark matter. c. copious amounts of dark energy. d. large amounts of dust. e. faulty pixels on the CCD camera. 13. The receding speed of spiral galaxies may also render their colors __________ due to __________________. a. bluer; relativistic beaming b. bluer; Doppler effect c. redder; relativistic beaming d. redder; Doppler effect e. redder; galactic interactions 14. 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 b. Type Ia supernovae c. globular clusters d. red giant stars e. RR Lyrae variables 15. Stars in the disks of spiral galaxies have orbits that are a. randomly oriented. b. constantly getting larger. c. mostly aligned in the same plane. d. spiral-shaped. e. unaffected by dark matter. 16. The nearest big galaxy, Andromeda, is at an estimated distance of a. 780 Mpc. b. 0.78 kpc. c. 0.78 Mpc. d. 2.5 × 106 kpc. e. 250 × 103 Mpc. 17. The disks of spiral galaxies appear blue because a. they are moving toward us. b. they contain a relatively high concentration of low-mass stars. c. they contain active regions of star formation. d. they contain more metals that, when ionized, emit blue light. Copyright © 2015 Pearson Canada Inc.

e. stars collide with each other frequently in these dense regions and explode as Type Ia supernovae. 18. Which of the following would not be found in an elliptical galaxy? a. low-mass stars b. Type Ia supernovae c. Type II supernovae d. planetary nebulae e. hot gas 19. To be a standard candle, an object must have a constant a. lifetime. b. brightness. c. luminosity. d. distance. e. mass.

20. According to Hubble’s law, as the distance of a galaxy ____________ its _______________ increases. a. increases; luminosity b. increases; recessional velocity c. decreases; luminosity d. decreases; recessional velocity e. decreases; peculiar velocity 21. Astronomers use galactic redshift to estimate a. gravity. b. luminosity. c. velocity. d. mass. e. distance. 22. Why can Type Ia supernovae be used to determine a galaxy’s distance? a. Type Ia supernovae occur only in very luminous galaxies. b. Most Type Ia supernovae have approximately the same luminosity. c. Most Type Ia supernovae have approximately the same size. d. A Type Ia supernova occurs in a typical galaxy about once every 100 years. e. Type Ia supernovae occur even in very small galaxies. 23. Which distance indicator can be used to measure the most distant objects? a. Cepheids b. Parallax c. Type Ia supernovae d. main-sequence fitting e. RR Lyrae stars 24. If the distance of a galaxy at a redshift z = 0.5 is 1,800 Mpc, how many years back into the past are we looking when we observe this galaxy? a. 500 million years b. 2 billion years c. 6 billion years d. 9 billion years e. 10 billion years 25. The spectra of most galaxies tell us that a. 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 their favorite wavelengths. d. galaxies in the past rotated at a faster rate than they do today. e. galaxies are rushing through space in all directions.

26. Which of the following lists distance indicators from nearest to farthest? a. Cepheids, parallax, main-sequence fitting, Type Ia supernovae b. parallax, main-sequence fitting, Cepheids, Type Ia supernovae c. parallax, main-sequence fitting, Type Ia supernovae, Cepheids d. main-sequence fitting, parallax, Cepheids, Type Ia supernovae e. Cepheids, Type Ia supernovae, main-sequence fitting, parallax 27. The Tully-Fisher method of determination of distances to galaxies is based on the correlation between a. color and redshift. b. star formation rate and morphological type. c. width of emission lines and black hole accretion rate. d. rotational speed and luminosity. e. dark matter radial profile and X-ray brightness.

28. Which galaxies are sometimes called “armless” disks? a. ellipticals b. irregulars c. dwarfs d. SOs e. barred spirals 29. Type Ia supernovae have an absolute magnitude of −19.3. If you discover a Type Ia supernovae in a distant galaxy that has an apparent magnitude of 22, then how far away is this galaxy? a. 0.3 Mpc b. 40 Mpc c. 1,200 Mpc d. 1,800 Mpc e. 3,500 Mpc 30. The nearest known quasar shows a redshift of z = 0.0516, which means it is at a distance of a. 220 Mpc. b. 450 Mpc. c. 100 Mpc. d. 15400 Mpc. e. 100 kpc. 31. For the more distant quasars, the emission lines that would normally occur in the visible domain would be shifted into a. UV. b. X-rays. c. gamma rays. d. IR. e. radio. 32. A certain spectral line of rest wavelength lrest (i.e., laboratory value) is shifted by 100 nm in a quasar. A second line with a rest wavelength half the (rest) value of the first one would be shifted by a. 200 nm. b. 100 nm. c. 500 nm. d. 50 nm. e. 1000 nm. 33. If a galaxy has an apparent velocity of 700 km/s, what is its distance if the Hubble constant is assumed to be 70 km/s/Mpc? a. 10 Mpc Copyright © 2015 Pearson Canada Inc.

vii

b. 70 Mpc c. 100 Mpc d. 700 Mpc e. 1,000 Mpc 34. If you found a galaxy with an Hα emission line that had a wavelength of 756.3 nm, what would be the galaxy’s redshift? (Note that the rest wavelength of the Hα emission line is 656.3 nm.) a. 0.05 b. 0.07 c. 0.10 d. 0.13 e. 0.15

35. If the distance of a galaxy is 10 Mpc, what is its recessional velocity if the Hubble constant is assumed to be 70 km/s/Mpc? a. 700 km/s b. 1,000 km/s c. 3,500 km/s d. 5,000 km/s e. 7,000 km/s 36. You see a galaxy in which the Hα line (rest wavelength = 656.3 nm) is observed at a wavelength of 756.3 nm. What would be the observed wavelength of a particular helium line that has a rest wavelength of 1,083 nm? a. 1,083 nm b. 1,183 nm c. 1,248 nm d. 1,440 nm e. 3,142 nm 37. If a galaxy has a recessional velocity of 50,000 km/s, at what wavelength will you observe the Hαemission line? (Note that the rest wavelength of the Hα emission line is 656.3 nm.) a. 695.7 nm b. 719.4 nm c. 742.3 nm d. 765.7 nm e. 1750 nm 38. If you found a galaxy with an Hα emission line that had a wavelength of 756.3 nm, what would be the galaxy’s distance if the Hubble constant is 70 km/s/Mpc? (Note that the rest wavelength of the Hα emission line is 656.3 nm.) a. 650 Mpc b. 760 Mpc c. 3,200 Mpc d. 6,400 Mpc e. 7,600 Mpc 39. 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 the Hubble constant is 70 km/s/Mpc. a. 720 Mpc b. 952 Mpc c. 1,166 Mpc d. 2,580 Mpc e. 3,730 Mpc 40. In the figure shown below, the upper spectrum is from hydrogen at rest in a laboratory, and

viii

the lower spectrum is from a galaxy. How far away is this galaxy? a. 110 Mpc b. 170 Mpc c. 230 Mpc d. 280 Mpc e. 340 Mpc 41. You read about the discovery of quasars with redshift z larger than 1. This means that a. their host galaxies are receding at speeds exceeding the speed of light. b. the measurements of redshift must be wrong, z cannot exceed 1. c. the relationship between z and receding speed must account for relativistic corrections. d. the speed of light can exceed c in the case of distant quasars. e. quasars must contain a lot of dark matter. 42. The rotation curve of a galaxy is a plot of the rotation speed as a function of the a. galaxyâ&#x20AC;&#x2122;s luminosity. b. mass of the dark matter halo. c. brightness of the luminous matter in the galaxy. d. radius from the center. e. ages of star clusters. 43. If you measure the velocity of a cloud of gas that is rotating around the center of a galaxy in a circular orbit with radius R, you can determine the a. total mass of the galaxy. b. mass of the stars and gas in the galaxy. c. mass of the galaxy enclosed within the radius R. d. mass of the galaxy located outside the radius R. e. mass of luminous matter within the radius R. 44. What makes up the majority of the mass of an individual spiral galaxy? a. a central supermassive black hole b. dark matter c. massive O- and B-type stars d. cold molecular gas clouds e. low-mass G-, K-, and M-type stars 45. Dust in galaxies does not count as dark matter because a. it absorbs only some wavelengths of light but not all wavelengths as dark matter does. b. it interacts with light. c. it is found only in spiral disks, whereas dark matter is also found in elliptical galaxies, too. d. dust is easily destroyed by dark matter. e. there is never enough to account for all the gravity in galaxies. 46. Dark matter is most likely made up of a. elementary particles that have mass but do not interact much with normal matter. b. supermassive black holes. c. faint stellar remnants such as white dwarfs and neutron stars. d. free-floating Jupiter-mass planets. e. cold concentrations of dust. 47. How have astronomers searched for evidence of MACHOs in the halo of the Milky Way? a. They search for stars that are binary companions of MACHOs. b. They search for rapidly moving, massive gas clouds. c. They search for disturbances in the background of gravitational waves. d. They search for distant stars with light briefly amplified by gravitational lensing. e. They search for close binary stars undergoing mass transfer. 48. The density of ordinary luminous matter can exceed the density of dark matter in which parts of galaxies? a. everywhere inside galaxies

b. only in the outer regions of galaxies c. only in star clusters d. near the centers of galaxies e. only around an AGN 49. Roughly what percentage of the total mass of a galaxy is made up of luminous, or normal, matter? a. 5–10 percent b. 25–30 percent c. 40–50 percent d. 70–75 percent e. 90–95 percent

50. How did astronomers determine that elliptical galaxies are composed mostly of dark matter? a. They measured the velocities of stars in the inner regions of the galaxies. b. They measured the rotation rates of gas as a function of distance from the centers of the galaxies. c. They measured the amount of gravitational pull elliptical galaxies have on companion galaxies. d. They assumed that the proportion of dark matter was roughly the same as in spiral galaxies. e. They measured the X-ray emission from hot gas gravitationally bound to the galaxies. 51. How can we measure the mass of an elliptical galaxy? a. by measuring the speeds of stars in the nucleus b. by observing the velocity of the hot, X-ray emitting gas that surrounds the galaxy c. by measuring the number of H II regions in the galaxy d. by measuring how many supernovae go off each century e. by measuring the amount of blue light in the galaxy 52. For which galaxies would it be easiest to measure rotation curves? a. elliptical b. face-on barred spirals c. face-on normal spirals d. face-on S0s e. edge-on spirals 53. If a galaxy had no dark matter, how would the velocity (v) of a star that orbited far outside the visible extent of the galaxy depend on its distance (r) from the center of the galaxy? Hint: Think about the Keplerian motion of planets around the Sun. a. v ∝ r−2 b. v ∝ r−1 c. d. v ∝ r e. v ∝ r2 54. Assume that when a supermassive black hole accretes gas, approximately 20 percent of the accreted mass is converted directly into energy, which is radiated away. If a quasar has a luminosity of 1013 L⊙, then what must be its mass accretion rate? a. 1 M⊙ per year b. 3.5 M⊙ per year c. 1 M⊙ per century d. 3.5 M⊙ per century e. 1 M⊙ per million years 55. Which of the following functions correctly illustrates the relation between mean density and black hole mass?

a. ρ ∝ M−2 b. ρ ∝ M−1 c. d. ρ ∝ M e. ρ ∝ M2

56. Scientists estimate that the efficiency of mass accretion onto a supermassive black hole is about 15 percent. Compared with the energetic efficiency of the stellar fusion of hydrogen into helium, the accretion is a. about 20 times more efficient. b. about 20 times less efficient. c. equally inefficient. d. twice as efficient. e. half as efficient. 57. AGNs are most likely powered by a. extremely dense star clusters. b. accreting supermassive black holes. c. ultradense molecular clouds. d. decaying dark matter. e. supernova explosions. 58. The unified model of AGN suggests that quasars, Seyfert galaxies, and radio galaxies are a. unrelated, although they are all very luminous galaxies at radio wavelengths. b. powered by similar mass accretion rates onto supermassive black holes. c. driven by violent mergers of two gas-rich spiral galaxies. d. similar phenomena but viewed from different orientation angles. e. all powered by high rates of star formation and supernova explosions. 59. In most cases it is impossible to observe the host galaxies of quasars because a. quasars outshine the host galaxies by a few orders of magnitude. b. the supermassive black holes have “eaten” all the stars in those galaxies. c. the host galaxies of quasars have too much dark matter. d. the host galaxies of quasars have too much obscuring dust. e. the galaxies hosting quasars are much smaller than our own Milky Way. 60. What happens to active galaxies when their AGNs run out of fuel? a. The black holes powering them collapse even further. b. They simply become normal galaxies. c. They slowly dissipate into clouds of gas and dust. d. They eventually pull in material from farther out, starting the AGN process all over again. e. They explode as gamma-ray bursts. 61. Quasars were first discovered in which region of the electromagnetic spectrum? a. X-ray b. gamma-ray c. radio d. infrared e. visible 62. What do the broad emission lines in quasar spectra tell astronomers about these objects? a. They are very far away. b. They are moving away from us. c. They have rapid internal motions. d. They are very dense. e. They have few heavy elements. .

63. How do we know that AGNs have sizes on the order of our Solar System? a. Quasars and Seyfert galaxies are stellarlike sources. b. Their brightness varies by factors of a few. c. The emission lines in their spectra show gas rotating at speeds of thousands of km/s. d. Their brightness varies on timescales ranging from hours to a day. e. We can measure their angular size, which gives us the physical size when we know the distance.

64. The formation of the Solar System and the existence of AGNs both demonstrate the a. importance of how luminosity varies with time. b. high efficiency of nuclear fusion. c. importance of accretion disks. d. importance of living in the center of a galaxy. e. existence of dark matter. 65. In some radio galaxies, we see only one side of the jet because a. the black hole produces a jet in only one direction. b. of relativistic beaming. c. the other side is inside the black hole’s event horizon. d. of dust obscuration. e. of dark matter that blocks the light from one side of the jet. 66. We interpret the presence of more AGNs in the past than today to indicate that a. there were fewer galaxy-galaxy interactions in the past. b. there were more galaxy-galaxy interactions in the past. c. supermassive black holes were larger in the past. d. today’s AGNs are hidden primarily by large amounts of cold gas and dust. e. AGNs had bigger central black holes in the past. 67. Quasars remain unresolved sources, even with the best telescopic observations, because they a. are too luminous. b. occupy a very small volume. c. are quite blue. d. produce copious amounts of radio energy. e. host supermassive black holes. 68. Which of these statements about quasars is false? a. Quasars are extremely luminous. b. Quasars are rare in our local vicinity. c. Quasars have high brightnesses. d. Quasars are extremely massive. e. Quasars are located at the centers of some active galaxies. 69. If a Seyfert galaxy’s nucleus varies in brightness on the timescale of 10 hours, then what is the approximate upper limit for the size of the emitting region? a. 20 AU b. 30 AU c. 50 AU d. 70 AU e. 120 AU 70. More luminous giant galaxies tend to have __________ supermassive black holes at their centers. a. more massive b. radio quiet c. more luminous d. slower rotating

xii

e. less massive

SHORT ANSWER 1. What determines the three-dimensional shapes of galaxies? 2. How do the current star formation rates of spiral and elliptical galaxies compare? 3. How did Hubble use his tuning fork diagram to classify galaxies? Is there any significance to this organization? 4. How do we know that the stellar disks in spiral galaxies are flat? How do we know that elliptical galaxies are not flat? 5. What were the positions taken by Heber Curtis and Harlow Shapley in their “Great Debate,” and how were both of them partially correct? 6. How did Edwin Hubble definitively prove that “spiral nebulae” were individual galaxies that were separate from the Milky Way? 7. The light curve of a Cepheid variable star allows astronomers to infer its mean apparent magnitude at 15.6 and the period of pulsation about 4.8 days. Utilizing the calibrated relation between period and luminosity for Classical Cepheids, its absolute magnitude is estimated at –3.6. What is the distance to that Cepheid star and, implicitly, the distance to its host galaxy? 8. Explain why the light gray bands (labeled Radar, Parallax, etc.) that cover certain ranges of distances in the figure shown below overlap with one another both at the beginning and at the end? 9. Name two “rungs” in the distance ladder that let us estimate the value of the Hubble constant. 10. Order the following objects by the maximum distance they can be detected: Cepheid variables, RR Lyrae stars, Type Ia supernovae, and low-mass main-sequence stars. Explain your reasoning.

11. Explain why the linear Hubble’s law has no free term.

xiii

12. The spectrum of a galaxy is observed to have an Hα emission line at a wavelength of 928.7 nm. What is its redshift? (Note that the rest wavelength of the Hα emission line is 656.3 nm.) 13. The spectrum of a galaxy is observed to have an Hα emission line at a wavelength of 856.3 nm. What is its distance if the Hubble constant is assumed to be 70 km/s/Mpc? (Note that the rest wavelength of the Hα emission line is 656.3 nm.) 14. What is the most likely candidate for making up the dark matter in galaxies? 15. How do we know that many elliptical galaxies contain significant amounts of dark matter? 16. What is plotted on a rotation curve, and what can it tell us about a galaxy? 17. If the rotational speed of the gas in the disk of a spiral galaxy is 100 km/s at a distance of 26,000 light-years from its center, then what is the mass enclosed within this radius? If the mass of luminous matter inside this radius is 5 billion M⊙ then what fraction of the galaxy’s mass is made of dark matter (within that same radius)? (Hint: Recall the technique learned earlier in Chapter 4.) 18. Outside the dark matter halo of a galaxy, how should the speed of an orbiting body such as a satellite dwarf galaxy depend on its distance from the giant galaxy’s center? 19. Estimate the total mass enclosed within 100 kpc radius, based on the rotation curve shown in the figure below. (Hint: Recall the technique learned earlier in Chapter 4.) 20. Microquasars are scaled-down versions of quasars, the former being powered by accretion onto stellar-sized black holes, the material being provided by a companion star. The underlying mechanism seems to be very similar in both microquasars and their supermassive AGN. Typical microquasars have luminosities that are ten orders of magnitude lower than ordinary quasars. What is the typical level of accretion rate in the two cases?

21. What are the main components of an AGN? 22. If there is a 4 million M⊙ black hole at the center of our galaxy, why is our own galaxy not an AGN? 23. How do we explain that “billions of galaxies are closer to Earth than is the nearest quasar”?

xiv

24. Give three examples of types of active galactic nuclei and give one reason why each is unique. 25. What is the difference between a Seyfert galaxy and a normal spiral galaxy? 26. How do astronomers know that AGNs are as small as our Solar System? 27. How does the appearance of an AGN depend on the viewing angle to the nucleus? 28. What is the connection between active galaxies and galactic mergers? 29. Why is a higher percentage of distant galaxies classified as AGNs compared with the percentage of galaxies around us locally? 30. If an AGN varies its brightness on a timescale of 4 hours, then what is the size limit of the AGN measured in AU?

For The Students Who Need Grade ‘A’ In Their Studies Hi, hope you are having a great day… We are a group of 24 writers having profound expertise in Business and Computer Science subjects. We can help you score A grade in your Accounting, Marketing, Finance, Economics, Management, Mathematics, Statistics, Information System, System Modeling, C++, Java Programming, Network Administration, Enterprise Administration, Database, Web Design, Networking, Internetworking, Data warehouse etc… We can also provide help with Psychology, Nursing, Health, History, English Literature, Political Science, Ethics, Humanity etc classes. We can help with essays, term papers, research papers, dissertation, Ilabs, mymatlab, Wileplus, quizzes, exams, discussion questions etc. You can expect: We understand each student has different requirement and we tend to treat each student according to his/her satisfaction. We will provide original assignments, plagiarism free and to custom requirement. We will always meet deadlines. Our support will be 24/27, even in holidays. Our pricing will be fair. We will do free revisions if you want to make changes in provided work. Email us for more information, query and quote.

WHISPERHILLS@GMAIL.COM