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Outline. Final next Monday (9:45). bring a scantron; good eraser, or extra scantron; sharp pencils calculator Dark Energy Review. Probable Job Opportunity.

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Outline

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  1. 1

  2. Outline • Final next Monday (9:45). • bring a scantron; good eraser, or extra scantron; sharp pencils • calculator • Dark Energy • Review 2

  3. 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. 3

  4. Test Topics (recent/new) • Chapter 13 - Neutron Stars and Black Holes • Shwarzschild radius • Chapter 14 - The Milky way • Size and Shape • Spectroscopic parallax • Cepheid variables • Mass and dark matter 4

  5. Test Topics (recent/new) • Chapter 15 - Normal and Active Galaxies • Standard Candles • Tully-Fisher relationship • Type I supernova • Quasars • Chapter 16 - Hubble’s Law and Dark Matter • Hubble’s law • Distance ladder • Large scale structure 5

  6. Test Topics (recent/new) • Chapter 17 - Cosmology • Big Bang • Age of the universe • Critical density & fate of universe 6

  7. Chapter 17 Cosmology 7

  8. Chapter 17Ultra Deep Field - more than 1000 galaxies are in this picture. Total estimate for the universe - ~40,000,000,000. 8

  9. Cosmology • How big is the universe? • How long has it been here? • How did it start? • How long will it last? 9

  10. The Fate of the Universe • Will it keep expanding forever? • Will gravity cause it to collapse? 10

  11. Figure 17.5Escape Velocity • With enough initial velocity, a spacecraft will “escape” from the Earth • With insufficient velocity, gravity will bring it back to Earth. 11

  12. Figure 17.6Model Universes 12

  13. The Fate of the Universe • A high density universe will collapse again into a Big Crunch. • A low density universe will continue to expand forever. • Critical density - boundary between the two cases. (9x10-27 kg/m3 = ~5 atoms/m3) • The ratio of the actual density to the critical density is called Wo, the critical density parameter. 13

  14. The Fate of the Universe • If you can determine the density of the universe, you can determine if there will be a Big Crunch or not. 14

  15. The Fate of the Universe • If you can determine the density of the universe, you can determine if there will be a Big Crunch or not. • However - most of the matter in the universe is dark! 15

  16. The Fate of the Universe • If you can determine the density of the universe, you can determine if there will be a Big Crunch or not. • However - most of the matter in the universe is dark! • Even with dark matter estimates, it appears that Wo < 1.0, if that is all you look at... 16

  17. The Accelerating Universe 17

  18. Figure 17.7Accelerating Universe • If the universe is “slowing down” because of gravity, distant objects (as seen in the past) should be moving faster. • Recent measurements show this is not the case - something is accelerating everything. • That “something” is called Dark Energy. • This “dark energy” is not understood at all. 18

  19. Discovery 17-1The Cosmological Constant 19

  20. Figure 17.8Cosmic Age 20

  21. http://www.newgrounds.com/portal/view/525347 21

  22. Current Status of the Universe • Expanding (and accelerating!) - looks like no big crunch for us. • Composition - looks like Wo=1, the critical density parameter. • Normal Matter ~ 4% • Mostly H and He • Dark Matter ~23% • Dark Energy ~73% 22

  23. Big Bang Events • Inflation - needed to get a uniform density in the universe. (<~10-32s!) • Nucleosynthesis - most of the He (~25% of normal matter) formed in the first 15 minutes of the universe. The rest was left as H. • Microwave Decoupling (atom formation) - once electrons joined the nuclei, then photons were no longer scattered and the universe became transparent. After a few 10,000s of years. • Large Scale Structure - normal matter “clumps” around the dark matter. • Finally acceleration by dark energy. 23

  24. The concept that on the grandest of scales, the universe is similar in appearance everywhere is: A) general relativity. B) special relativity. C) homogeneity. D) isotropy. E) universality. 24

  25. The concept that on the grandest of scales, the universe is similar in appearance everywhere is: A) general relativity. B) special relativity. C) homogeneity. D) isotropy. E) universality. 25

  26. ADT 26

  27. How confident were you about your answers on the Astronomy Diagnostic Test A) very confident. B) somewhat confident. C) not very confident. D) just guessing. 27

  28. Why is it cold at the North Pole, even during northern hemisphere summer? 1 - Because the “pole” itself doesn’t point very close to the direction of the Sun 2 - Because there are fewer daylight hours at the pole than at lower latitudes (e.g., Durango) 3 - Because of the high altitude at the pole 4 -Because the pole is further away from the Sun than lower latitudes are (e.g., Durango) 28

  29. Why is it cold at the North Pole, even during northern hemisphere summer? 1 - Because the “pole” itself doesn’t point very close to the direction of the Sun 2 - Because there are fewer daylight hours at the pole than at lower latitudes (e.g., Durango) 3 - Because of the high altitude at the pole 4 -Because the pole is further away from the Sun than lower latitudes are (e.g., Durango) 29

  30. Star A has a parallax shift of 0.4 arc secondStar B has a parallax shift of 0.6 arc seconds 1: B is 1.5 times as far away as A 2: Star A is at a distance of 4 parsecs (pc) 3: Star B is at a distance of 1.66 parsecs (pc) 4: Star A is 0.4 times as far away as B 30

  31. Star A has a parallax shift of 0.4 arc secondStar B has a parallax shift of 0.6 arc seconds 1: B is 1.5 times as far away as A 2: Star A is at a distance of 4 parsecs (pc) 3: Star B is at a distance of 1.66 parsecs (pc) 4: Star A is 0.4 times as far away as B 31

  32. Which is correct? 1 - The new moon rises at noon. 2 - The first quarter moon rises at noon. 3 - The full moon rises at noon. 4 - The third quarter moon rises at noon. 32

  33. Which is correct? 1 - The new moon rises at noon. 2 - The first quarter moon rises at noon. 3 - The full moon rises at noon. 4 - The third quarter moon rises at noon. 33

  34. In Paris, France (50 degrees north latitude), what is the longest day of the year? 1: March 21 2: June 21 3: September 21 4: December 21 34

  35. In Paris, France (50 degrees north latitude), what is the longest day of the year? 1: March 21 2: June 21 3: September 21 4: December 21 35

  36. Where along the horizon does the Sun rise on June 21 in Paris, France? 1: Due east 2: North of east 3: South of east 4: Can’t tell with information given 36

  37. Where along the horizon does the Sun rise on June 21 in Paris, France? 1: Due east 2: North of east 3: South of east 4: Can’t tell with information given 37

  38. Where along the horizon does the Sun rise on June 21 in Sydney, Australia? 1: Due east 2: North of east 3: South of east 4: Can’t tell with information given 38

  39. Where along the horizon does the Sun rise on June 21 in Sydney, Australia? 1: Due east 2: North of east 3: South of east 4: Can’t tell with information given 39

  40. On December 21, in Durango, if there is a full moon, where does it rise? 1: Due east 2: Almost due east (within 5 degrees) 3: South of east (by more than 5 degrees) 4: North of east (by more than 5 degrees) 40

  41. On December 21, in Durango, if there is a full moon, where does it rise? 1: Due east 2: Almost due east (within 5 degrees) 3: South of east (by more than 5 degrees) 4: North of east (by more than 5 degrees) 41

  42. On December 21, in Australia, if there is a full moon, where does it rise? 1: Due east 2: Almost due east (within 5 degrees) 3: South of east (by more than 5 degrees) 4: North of east (by more than 5 degrees) 42

  43. On December 21, in Australia, if there is a full moon, where does it rise? 1: Due east 2: Almost due east (within 5 degrees) 3: South of east (by more than 5 degrees) 4: North of east (by more than 5 degrees) 43

  44. A 5 meter (diameter) telescope 1 : gathers 5 times as much light as a 1 m telescope 2 : gathers 1/2 as much light as a 10 m telescope 3 : gathers 4 times as much light as a 2.5 m telescope 4 : gathers 5/2 as much light as a 2 m telescope 44

  45. A 5 meter (diameter) telescope 1 : gathers 5 times as much light as a 1 m telescope 2 : gathers 1/2 as much light as a 10 m telescope 3 : gathers 4 times as much light as a 2.5 m telescope 4 : gathers 5/2 as much light as a 2 m telescope 45

  46. Which statement about planetary orbits is incorrect? A) All planets orbit the Sun counterclockwise. B) Most stay close to the earth's equator in the sky. C) Most orbits are almost circular, with low eccentricities. D) All have the Sun at one focus of their elliptical orbits. E) Most also rotate counterclockwise on their axes as well. 46

  47. Which statement about planetary orbits is incorrect? A) All planets orbit the Sun counterclockwise. B) Most stay close to the earth's equator in the sky. C) Most orbits are almost circular, with low eccentricities. D) All have the Sun at one focus of their elliptical orbits. E) Most also rotate counterclockwise on their axes as well. 47

  48. Iron meteorites are believed to come from: A) the core of a differentiated asteroid, now broken up. B) the crust of a differentiated asteroid, now broken up. C) a broken up cometary nucleus. D) debris from the Kuiper Belt. E) interstellar space. 48

  49. Iron meteorites are believed to come from: A) the core of a differentiated asteroid, now broken up. B) the crust of a differentiated asteroid, now broken up. C) a broken up cometary nucleus. D) debris from the Kuiper Belt. E) interstellar space. 49

  50. Long-period comets are believed to originally come from: A) the asteroid belt. B) the Kuiper belt. C) the Oort cloud. D) the satellite system of Jupiter. E) the interstellar medium. 50

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