1. REMINDERS Exam II next Thursday, April 14! Practice exam will be posted on website - Same format as first exam – Multiple Choice & Short Answer Review session (Q & A only) Tuesday, April 12 @ 7 pm Location: normal lecture hall in Physics

2. Discussion Review Plan 1.Study techniques suggestions 2.Chapters covered 3.Main equations to know (partial list!) 4.Key things to know (partial list!) 5.Practice discussion questions 6.Practice multiple choice

3. Study Techniques Take notes on your notes – make summary sheets Make these into flash cards & study (not just definitions and equations – concepts, too!) Draw pictures! Having these things will make studying for the final easier Think about possible essay questions and be prepared for them!

4. Material Covered Chapter 5 – Light, interaction with matter, telescopes Chapter 10 – The Sun Chapter 11 – Stars – overview / properties Chapter 12 – Stellar evolution Chapter 13 – Deaths of stars Textbook, lecture notes, discussion section activities!

5. Equations to Be Familiar With (may be an incomplete list!) E = hc / λ photon T ~ 1 / λ peak distance = 1 / parallax angle Luminosity, L ~ R 2 T 4 Brightness or Flux, F ~ L / (distance) 2

6. Key Things to Know: (definitely an incomplete list!) Equations already mentioned EM spectrum – order of wavelength regions Types of spectra & how they are formed Doppler Effect Structure of our SUN H fusion – (4 H → 1 He + energy + neutrinos) Spectral types, OBAFGKM

7. Key Things to Know (continued): Binaries – how to get masses, which are stable? HR diagram – be able to draw it and label Life cycle of low & high mass stars Hydrostatic Equilibrium Stellar mass cutoffs – 2M, 8 M, 1.4 M, 3 M (M is the mass of the Sun)

8. Practice Questions

9. The electromagnetic spectrum Figure 3.5 Identify the following portions of the Electromagnetic spectrum: A B D E C

10. The electromagnetic spectrum Figure 3.5 Which end of the spectrum is more energetic, A or B? Why? A B

11. Light has a DUAL NATURE! “photon” wave & Energy of photon = hc / λ

12. If the Hydrogen gas cloud is moving towards Earth, the absorption line marked will shift in which direction? BA An absorption line of Hydrogen measured at rest

13. How do light and matter interact? KNOW THESE DEFINITIONS! Emission Absorption Transmission Reflection or Scattering

14. Electromagnetic radiation Figure 3.8 What does this diagram illustrate?

15. What types of light spectra can we observe? 1. Continuous spectra 2. Absorption spectra 3. Emission spectra

16. Which is the absorption spectrum?

17. Which is the continuous spectrum?

18. Which is the emission spectrum?

19. How spectra are produced – electron transitions

20. BLUE Yellow RED BLACK Which spectrum is coming from the coolest object?

21. BLUE Yellow RED BLACK The object producing the yellow spectrum might be what type of star?

22. BLUE Yellow RED BLACK Is the star producing the yellow or red spectrum hotter? Why?

23. BLUE Yellow RED BLACK Which spectrum is coming from the hottest object?

24. Which star is more luminous? T = 15,000 K Radius = 1 unit T = 15,000 K Radius = 2 units

25. Which star is more luminous? T = 3,000 K Radius = 1 unit T = 15,000 K Radius = 1 unit

26. REMEMBER! Luminosity of a star is intrinsic. Depends on Temperature & Radius. L ~ R 2 T 4 Flux changes with distance. F ~ L / d 2

27. For which stars would we observe a Doppler Shift? A B C

28. Doppler shift Figure 3.18

29. Doppler Effect Summary Motion toward or away from an observer causes a shift in the observed wavelength of light: blueshift (shorter wavelength)  motion _______ you redshift (longer wavelength)  motion AWAY from you greater shift  greater speed

30. Doppler Effect Summary Motion toward or away from an observer causes a shift in the observed wavelength of light: blueshift (shorter wavelength)  motion toward you redshift (longer wavelength)  motion ______ from you greater shift  greater speed

31. How do telescopes help us learn about the universe? Telescopes collect more light than our eyes  light-collecting area Telescopes can see more detail than our eyes  angular resolution Telescopes/instruments can detect light that is invisible to our eyes (e.g., infrared, ultraviolet)

32. Angular Resolution The minimum angular separation that the telescope can distinguish.

33. Are the emission lines located in the UV part of the spectrum or the IR part of the spectrum?

34. Is it on FIRE? Which is the correct explanation for the sun’s shining? Is it CONTRACTING? Is it powered by NUCLEAR ENERGY?

35. E = mc 2 - Einstein, 1905 What does Einstein’s famous equation mean? How can we apply it to the Sun?

36. The balance of the inward force of gravity with the outward force of pressure due to radiation is referred to as ?

37. Solar wind A) Corona B) Chromosphere C) Photosphere D) Core

38. What enables nuclei to overcome repulsion and get close enough to fuse in the core of a star?

39. Sun releases energy by fusing four hydrogen nuclei into what? What will the next fusion product be? ?

40. IN 4 protons OUT 4 He nucleus 2 positrons 2 gamma rays 2 _______???? Total mass is 0.7% lower Where does it go?

41. Why do sunspots appear dark on the surface of the sun?

42. Solar Thermostat Temperature Restored Temperature Decreases Fusion Rate (Increases or Decreases)? Core (compresses or expands)?

43. Practice Multiple Choice Questions

44. A difference between an ultraviolet photon and a radio photon is that A. the energy of the radio photon is greater B. only the radio photon is an electromagnetic wave C. only the ultraviolet photon is an electromagnetic wave D. the energy of the ultraviolet photon is greater E. none of the answers are correct

45. A difference between an ultraviolet photon and a radio photon is that A. the energy of the radio photon is greater B. only the radio photon is an electromagnetic wave C. only the ultraviolet photon is an electromagnetic wave D. the energy of the ultraviolet photon is greater E. none of the answers are correct

46. The speed of a radio wave is A. the speed of sound B. slower than the speed of light C. slower than the speed of sound D. the speed of light E. none of the above

47. The speed of a radio wave is A. the speed of sound B. slower than the speed of light C. slower than the speed of sound D. the speed of light E. none of the above

48. The sun A. is composed of ionized gas that is mostly neon B. is composed of molecular gas that is mostly neon C. is composed of ionized gas that is mostly hydrogen D. is composed of molecular gas that is mostly hydrogen

49. The sun A. is composed of ionized gas that is mostly neon B. is composed of molecular gas that is mostly neon C. is composed of ionized gas that is mostly hydrogen D. is composed of molecular gas that is mostly hydrogen

50. The energy source for the sun is A. combustion of hydrocarbons B. solar flares C. nuclear fission, the splitting of two hydrogen atoms D. nuclear fusion, the joining of two hydrogen atoms E. combustion of hydrogen

51. The energy source for the sun is A. combustion of hydrocarbons B. solar flares C. nuclear fission, the splitting of two hydrogen atoms D. nuclear fusion, the joining of two hydrogen atoms E. combustion of hydrogen

52. The layer of the sun that emits most of the light we see is A. the corona B. the chromosphere C. the photosphere D. none of the answers are correct

53. The layer of the sun that emits most of the light we see is A. the corona B. the chromosphere C. the photosphere D. none of the answers are correct

54. Electromagnetic radiation from astronomical objects can be studied from the surface of the Earth in which part of the spectrum? A. gamma-rays B. x-rays C. radio

55. Electromagnetic radiation from astronomical objects can be studied from the surface of the Earth in which part of the spectrum? A. gamma-rays B. x-rays C. radio

56. The hotter an object A. the brighter it appears at all wavelengths, and the longer the wavelength at which it appears brightest B. the shorter the wavelength at which it appears brightest C. The brighter it appears at all wavelengths, and the shorter the wavelength at which it appears brightest D. the longer the wavelength at which it appears brightest E. the brighter it appears at all wavelengths

57. The hotter an object A. the brighter it appears at all wavelengths, and the longer the wavelength at which it appears brightest B. the shorter the wavelength at which it appears brightest C. The brighter it appears at all wavelengths, and the shorter the wavelength at which it appears brightest D. the longer the wavelength at which it appears brightest E. the brighter it appears at all wavelengths

58. Heat affects wavelength Figure 3.6

59. An object emits an emission line spectrum. If the object moves towards an observer, A. the observed emission lines shift to shorter wavelengths B. the observed emission lines shift to longer wavelengths C. the emission line spectrum shifts to a continuous spectrum D. the emission line spectrum shifts to an absorption line spectrum

60. An object emits an emission line spectrum. If the object moves towards an observer, A. the observed emission lines shift to shorter wavelengths B. the observed emission lines shift to longer wavelengths C. the emission line spectrum shifts to a continuous spectrum D. the emission line spectrum shifts to an absorption line spectrum

61. The hottest part of the solar atmosphere A. found in sunspots B. is the photosphere C. is the corona D. is the chromosphere

62. The hottest part of the solar atmosphere A. found in sunspots B. is the photosphere C. is the corona D. is the chromosphere

63. Which of the following is ordered by increasing wavelength? A. infrared, visible, radio, gamma-ray B. visible, infrared, radio, gamma-ray C. gamma-ray, visible, infrared, radio D. radio, visible, infrared, gamma-ray

64. Which of the following is ordered by increasing wavelength? A. infrared, visible, radio, gamma-ray B. visible, infrared, radio, gamma-ray C. gamma-ray, visible, infrared, radio D. radio, visible, infrared, gamma-ray

65. An atom is ionized if A. it has lost a proton B. it has lost an electron C. it has lost a neutron D. it has absorbed a photon

66. An atom is ionized if A. it has lost a proton B. it has lost an electron C. it has lost a neutron D. it has absorbed a photon

67. Sunspots appear darker than the surrounding photosphere because A. they have a carbonaceous composition B. they have an icy composition C. they are cooler than their surroundings D. they are shadowed from coronal radiation

68. Sunspots appear darker than the surrounding photosphere because A. they have a carbonaceous composition B. they have an icy composition C. they are cooler than their surroundings D. they are shadowed from coronal radiation

69. High mass stars have shorter lifetimes than low mass stars because high mass stars A. have luminosities that are far larger than low mass stars B. have less hydrogen than low mass stars C. have less helium than low mass stars D. release less energy per nuclear reaction than low mass stars

70. High mass stars have shorter lifetimes than low mass stars because high mass stars A. have luminosities that are far larger than low mass stars B. have less hydrogen than low mass stars C. have less helium than low mass stars D. release less energy per nuclear reaction than low mass stars

71. If the Sun were replaced by a black hole of the same mass, A. a great sucking sound would be heard B. the Earth would continue to orbit pretty much as it does now C. the Earth would fall directly towards the black hole D. the Earth would spiral into the black hole over the next 1000 years

72. If the Sun were replaced by a black hole of the same mass, A. a great sucking sound would be heard B. the Earth would continue to orbit pretty much as it does now C. the Earth would fall directly towards the black hole D. the Earth would spiral into the black hole over the next 1000 years

73. The most common stars are A. lower main sequence stars B. supergiants C. giants D. upper main sequence stars E. neutron stars

74. The most common stars are A. lower main sequence stars B. supergiants C. giants D. upper main sequence stars E. neutron stars

75. Main sequence stars A. are stars which have no hydrogen or helium B. have nuclear fusion of hydrogen occurring in their cores C. are stars which are mostly made of hydrogen D. are stars found in spiral arms

76. Main sequence stars A. are stars which have no hydrogen or helium B. have nuclear fusion of hydrogen occurring in their cores C. are stars which are mostly made of hydrogen D. are stars found in spiral arms

77. A planetary nebula is A. produced by a supernova explosion B. a nebula within which planets are forming C. the expelled outer envelope of a medium mass star D. a cloud of hot gas surrounding a planet

78. A planetary nebula is A. produced by a supernova explosion B. a nebula within which planets are forming C. the expelled outer envelope of a medium mass star D. a cloud of hot gas surrounding a planet

79. The density of a __________ is greater than the density of a ___________. A. neutron star, black hole B. pulsar, neutron star C. pulsar, white dwarf D. white dwarf, pulsar E. white dwarf, black hole

80. The density of a __________ is greater than the density of a ___________. A. neutron star, black hole B. pulsar, neutron star C. pulsar, white dwarf D. white dwarf, pulsar E. white dwarf, black hole

81. Which star is more luminous? T = 3,000 K Radius = 7 units T = 12,000 K Radius = 1 unit