Large Scale Structure

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3. Large Scale Structure 3

4. Outline • Homework (don’t forget them) • Final Monday, 9:45. • bring a scantron; good eraser, or extra scantron; sharp pencils • calculator • Review Hubble’s Law • Large Scale Structure 4

5. Probable Job Opportunity • The Academic Success Program regularly funds Astronomy Tutors/ Study Group leaders. If you might be interested in this for next fall, please let me know via email. 5

6. The Tully-Fisher Relation exists between the galaxy's luminosity and its: A) color. B) size. C) age. D) rotation. 6

7. The Tully-Fisher Relation exists between the galaxy's luminosity and its: A) color. B) size. C) age. D) rotation. 7

8. What method would be most appropriate to determine the distance to a nearby galaxy? A) Spectroscopic parallax B) Cepheid variables C) Hubble’s law D) Radar ranging 8

9. What method would be most appropriate to determine the distance to a nearby galaxy? A) Spectroscopic parallax B) Cepheid variables C) Hubble’s law D) Radar ranging 9

10. Large-Scale Structure 10

11. Figure 16.3Cosmic Distance Ladder 11

12. Large-Scale Structure • Use the scale of 1m = 1 A.U. 12

13. Large-Scale Structure • Use the scale of 1m = 1 A.U. • The Earth is 1 m from the Sun 13

14. Large-Scale Structure • Use the scale of 1m = 1 A.U. • The Earth is 1 m from the Sun • The Nearest star is near Albuquerque 14

15. Large-Scale Structure • Use the scale of 1m = 1 A.U. • The Earth is 1 m from the Sun • The Nearest star is near Albuquerque • The center of the Milky Way galaxy would be 4 times as far as the moon. 15

16. Large-Scale Structure • Use the scale of 1m = 1 A.U. • The Earth is 1 m from the Sun • The Nearest star is near Albuquerque • The center of the Milky Way galaxy would be 4 times as far as the moon. • The Andromeda galaxy would be near Mars 16

17. Figure 16.3Cosmic Distance Ladder 17

18. Large-Scale Structure • Redshift surveys of galaxies are used to determine the large-scale structure of the universe. 18

19. Figure 16.9First Galaxy Survey from the mid-1980’s 19

20. Figure 16.10The Local Universe 20

21. Large-Scale Structure • Redshift surveys of galaxies are used to determine the large-scale structure of the universe. • Observed structure includes: • Strings • Filaments • Voids • The most likely explanation is a slice through “Bubbles.” • Only a few of these “slices” have been completed. 21

22. Figure 17.1Galaxy Survey 22

23. Galaxy Survey • The universe is homogeneous - it looks the same everywhere • The universe is isotropic - it looks the same in all directions • Cosmological principle - the universe is isotropic and homogeneous. 23

24. Tools to study structure.. 24

25. Central Black Hole • http://www.astro.ucla.edu/~ghezgroup/gc/pictures/orbitsMovie.shtml • ~4x106 Solar Masses 25

26. Quasars 26

27. Quasars • Quasars are the active nuclei of very distant galaxies. (Cannot observe the “rest” of the quasar’s galaxy.) • Energy output ~1000x Milky Way. • Powered by material accreting onto a supermassive black hole. • Very large redshifts = Very distant. • Can use spectra to study closer material. 27

28. Figure 16.12Twin Quasar 28

29. Figure 16.13Gravitational Lens 29

30. Figure 16.14Einstein Cross 30

31. Figure 16.15Galaxy Cluster Lensing 31

32. Figure 16.16Dark Matter Map 32

33. Figure 16.11Absorption Line “Forest” 33

34. Review Questions 34

35. RR Lyrae stars helped astronomers to: A) Find the distance to nearby galaxies B) Determine the center of the Milky Way C) Verify spectroscopic parallax D) Complete the H-R diagram 35

36. RR Lyrae stars helped astronomers to: A) Find the distance to nearby galaxies B) Determine the center of the Milky Way C) Verify spectroscopic parallax D) Complete the H-R diagram 36

37. What does the Hubble constant measure? A) The density of galaxies in the universe B) The luminosity of distant galaxies C) The rate of expansion of the universe D) the speed of a galaxy of known redshift E) the reddening of light by intergalactic dust clouds 37

38. What does the Hubble constant measure? A) The density of galaxies in the universe B) The luminosity of distant galaxies C) The rate of expansion of the universe D) the speed of a galaxy of known redshift E) the reddening of light by intergalactic dust clouds 38

39. What method would not be appropriate to determine the distance to a nearby galaxy? A) Tully-Fisher relationship B) Cepheid variables C) Hubble’s law D) Type I Supernovae 39

40. What method would not be appropriate to determine the distance to a nearby galaxy? A) Tully-Fisher relationship B) Cepheid variables C) Hubble’s law D) Type I Supernovae 40

41. Olber’s Paradox 41

42. Olber’s Paradox • Why isn’t the sky bright? • If the universe is infinite, no matter which way you look, you should see a star. 42

43. Figure 17.2Olbers’s Paradox 43

44. Olber’s Paradox • Why isn’t the sky bright? • If the universe is infinite, no matter which way you look, you should see a star. • Since the sky is not bright, either… • Universe is finite. • Universe evolves with time. 44

45. The Big Bang • At some time in the past, everything was at a single point. 45

46. The Big Bang • At some time in the past, everything was at a single point. • When - Approximately 14 billion years ago. • The Big Bang provides the resolution of Olber’s Paradox 46

47. Figure 17.3Receding Galaxies - where was the Big Bang? • The Big Bang happened everywhere at once. 47

48. Chapter 17Ultra Deep Field - more than 1000 galaxies are in this picture. Total estimate for the universe - ~40,000,000,000. 48

49. Chapter 17 Cosmology 49

50. Cosmology • How big is the universe? • How long has it been here? • How did it start? • How long will it last? 50