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Solar Interior/ Nuclear Fusion

Solar Interior/ Nuclear Fusion. Outline. Solar interior Fusion Solar evolution Stars. Tutoring. Wednesday 4:30-6:00 Berndt 640 USE IT OR LOSE IT. Review. Sunspots… are darker because they are actually cooler than the rest of the Sun the result of a “ kink ” in the magnetic field

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Solar Interior/ Nuclear Fusion

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  1. 1

  2. Solar Interior/ Nuclear Fusion 2

  3. Outline • Solar interior • Fusion • Solar evolution • Stars 3

  4. Tutoring • Wednesday 4:30-6:00 • Berndt 640 • USE IT OR LOSE IT 4

  5. Review • Sunspots… • are darker because they are actually cooler than the rest of the Sun • the result of a “kink” in the magnetic field • size of Earth; usually come in pairs • magnetic field switches every 11 year; cycle is 22 years • Maunder minimum corresponded to mini ice age 5

  6. Review • and… • The solar equator rotates faster than the poles • the Zeeman effect is a splitting of spectral lines from magnetic fields • sunspots magnetic field is about 1000x greater than the surrounding area • solar wind is the sun evaporating 6

  7. As the Sun rotates, an individual sunspot can be tracked across its face. From Eastern to Western limb, this takes about: A) 12 hours B) A week C) Two weeks D) A month E) 5.5 years 7

  8. As the Sun rotates, an individual sunspot can be tracked across its face. From Eastern to Western limb, this takes about: A) 12 hours B) A week C) Two weeks D) A month E) 5.5 years 8

  9. Compared to the Earth, the Sun’s average density is: A) lower B) about the same C) much greater 9

  10. Compared to the Earth, the Sun’s average density is: A) lower B) about the same C) much greater 10

  11. From inside out, which is the correct order? A) core, convective zone, radiative zone B) photosphere, radiative zone, corona C) radiative zone, convective zone, chromosphere D) core, chromosphere, photosphere E) convective zone, radiative zone, granulation 11

  12. Solar Atmosphere • Photosphere - • What we see. (~5780 K) • Chromosphere - • pinkish color (from Ha line); can see during eclipse. • cooler temperature (~4500 K) • Transition zone/Corona - • Shift from absorption spectrum to emission spectrum • Corona very hot (~3 million K) • Solar Wind - • The Sun is evaporating! 12

  13. Figure 9.10Solar Chromosphere 13

  14. Figure 9.12Solar Corona 14

  15. Figure 9.24Active Corona 15

  16. Figure 9.13Solar Atmospheric Temperature 16

  17. What about the internal structure? 17

  18. Solar Composition 18

  19. Figure 9.2Solar Structure 19

  20. Internal Structure • Core - • temperatures hot enough for nuclear reactions (~15 million K) • Radiation Zone - • Temperatures cooler, so no nuclear reactions. • Hot enough so everything is ionized. • Atoms can’t absorb photons. • Convection Zone - • Temperature cooler. • Atoms form and can absorb radiation. 20

  21. Figure 9.6Solar Interior 21

  22. How do we know what is inside the Sun? 22

  23. How do we know what is inside the Sun? • Standard model 23

  24. Figure 9.4Stellar Balance 24

  25. Figure 9.5Solar Oscillations 25

  26. Figure 9.7Solar Convection 26

  27. Figure 9.8Solar Granulation 27

  28. Figure 9.11Solar Spicules • dynamic jets • 5-10 minute life • possibly related to seismic activity 28

  29. Typically, a granule in the photosphere of the sun is about the size of? A) A city, ~20-30 kilometers across. B) Texas, ~1000 km across. C) The Earth, ~12,000 km across. D) Jupiter, ~100,000 km across. 29

  30. Typically, a granule in the photosphere of the sun is about the size of? A) A city, ~20-30 kilometers across. B) Texas, ~1000 km across. C) The Earth, ~12,000 km across. D) Jupiter, ~100,000 km across. 30

  31. From inside out, which is the correct order? A) core, convective zone, radiative zone B) photosphere, radiative zone, corona C) radiative zone, convective zone, chromosphere D) core, chromosphere, photosphere E) convective zone, radiative zone, granulation 31

  32. From inside out, which is the correct order? A) core, convective zone, radiative zone B) photosphere, radiative zone, corona C) radiative zone, convective zone, chromosphere D) core, chromosphere, photosphere E) convective zone, radiative zone, granulation 32

  33. Misc notes • Problem 9.1 • Should say “Section 9.1” and NOT 16.1. • And note that Mercury’s orbit is very eccentric, so you can’t simply use the semi-major axis for it’s distance at perihelion. 33

  34. 34

  35. Nuclear Fusion 35

  36. Forces in Nature • Gravity - long range; relatively weak. • Electromagnetic - long range; responsible for atomic interactions (chemistry) • Weak Nuclear Force - short range; responsible for some radioactive decay • Strong Force - short range; holds nuclei together 36

  37. Nuclear Fusion • Combining light nuclei into heavy ones. nucleus 1 + nucleus 2 = nucleus 3 + energy • Law of conservation of mass and energy E = mc2 37

  38. Figure 9.25Proton Interactions • Like charges (two protons) repel by electromagnetic force. • With enough energy (temperature) and pressure, can overcome EM force 38

  39. Proton-Proton chain • Most common reaction in the Sun. 4 protons ==>> helium-4 + 2 neutrinos + energy • Many other reactions are possible, but 90% are the proton-proton chain. • Calculate energy produced from mass differences. (use E=mc2), get 4.3x10-12 J (Joules) when 4 protons fuse to Helium. • From Sun’s luminosity, can calculate that 600 million tons of Hydrogen per second are fused into Helium. 39

  40. Figure 9.26Solar Fusion 40

  41. Proton-Proton chain • Neutrinos - “little neutral one” are almost mass-less, and react with almost nothing. 41

  42. Figure 9.27Neutrino Telescope - Super Kamiokande • Need large amounts of matter to detect neutrinos • Solar Neutrino Problem - until recently could not explain observed low numbers. 42

  43. Proton-Proton chain • Neutrinos “oscillations” explain the observation discrepancy. • Neutrinos take eight minutes to get to the Earth from the Sun. • In that time they can mutate (oscillate) into other forms. 43

  44. Three Minute Paper • Write 1-3 sentences. • What was the most important thing you learned today? • What questions do you still have about today’s topics? 44

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