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Solar Interior/ Nuclear Fusion

Solar Interior/ Nuclear Fusion. Outline. Solar interior Fusion Solar evolution Stars. 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

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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. 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 4

  5. 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 5

  6. 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 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. Compared to the Earth, the Sun’s average density is: A) lower B) about the same C) much greater 8

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

  10. 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 10

  11. What about the internal structure? 11

  12. Solar Composition 12

  13. Figure 9.2Solar Structure 13

  14. What about the internal structure? • Core - • temperatures hot enough for nuclear reactions • 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. 14

  15. Figure 9.6Solar Interior 15

  16. How do we know what is inside the Sun? 16

  17. How do we know what is inside the Sun? • Standard model 17

  18. Figure 9.4Stellar Balance 18

  19. Figure 9.5Solar Oscillations 19

  20. Figure 9.7Solar Convection 20

  21. Figure 9.8Solar Granulation 21

  22. Figure 9.11Solar Spicules • dynamic jets • 5-10 minute life • possibly related to seismic activity 22

  23. 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. 23

  24. 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. 24

  25. 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 25

  26. 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 26

  27. Misc notes • Problem 9.1 - note that Mercury’s orbit is very eccentric, so you can’t simply use the semi-major axis for it’s distance at perihelion. 27

  28. 28

  29. Nuclear Fusion 29

  30. 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 30

  31. Nuclear Fusion • Combining light nuclei into heavy ones. nucleus 1 + nucleus 2 = nucleus 3 + energy • Law of conservation of mass and energy E = mc2 31

  32. Figure 9.25Proton Interactions • Like charges (two protons) repel by electromagnetic force. • With enough energy (temperature) and pressure, can overcome EM force 32

  33. 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. 33

  34. Figure 9.26Solar Fusion 34

  35. Proton-Proton chain • Neutrinos - “little neutral one” are almost mass-less, and react with almost nothing. 35

  36. 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. 36

  37. 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. 37

  38. 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? 38

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