1. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1 Announcements: Spring Break: next week!! Exam #2: Thursday, April 5 th ! Chp. 3, 11

3. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 3 The Sun produces its energy from a)Electric currents generated in its core b)Chemical reactions (oxidation reactions) producing flames c)Fusion of hydrogen into helium d)Disintegration of helium into hydrogen

4. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 4 The Sun as a Star (Chp. 11)

5. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 5 About how many years elapse between times of maximum solar activity? a)30 b)11 c)22 d)1 e)None of the above.

6. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 6 The Butterfly Diagram plots a) Number of sunspots as a function of time b) Number of sunspots as a function of magnetic field strength c) Rotation rate as a function of latitude d) Sunspot position as a function of time.

7. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 7 Solar Cycle The number of sunspots varies in an 11 year cycle Each sunspot peak is called a solar maximum

8. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 8 Butterfly Diagram

9. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 9 Maunder Minimum 1645-1715: extended lull in solar activity “Little Ice Age” recorded in Europe

10. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 10 The Sun-Earth Connection

11. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 11 http://solar-center.stanford.edu/sun-on-earth/glob-warm.html

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13. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 13 Geomagnetic: redSolar: blue Sun-Earth Connection

14. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 14 Which of the following about the sunspot cycle is not true? a) The number of spots rises and falls every 11 years. b) The pattern of the magnetic polarity of the spots repeats every 22 years. c) spots are located in regions of high magnetic activity d) spots are more readily seen near the rotational poles of the Sun where magnetic field lines are concentrated

15. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 15 The Magnetic Field of the Sun Current loop

16. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 16 Differential Rotation plays important role in 11-year cycle: Rotation period at equator: 25 days Rotation period at poles: 36 days

17. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 17 What Powers the Sun? 1.Early Ideas 2.Modern Ideas 3.Fusion 4.How energy is transferred Conduction, Convection, Radiation 5.Hydrostatic Equilibrium 6. Lifetime of the Sun

18. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 18 Early Ideas The Sun is a ball of fire. Problem #1: A lump of coal the size of the Sun would burn out in about 5000 years. Problem #2: Temperatures involved are much too high for common fire which is a chemical process involving the electrons orbiting molecules.

19. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 19 Early Ideas (cont) Gravity compresses interior of Sun to extreme temperatures. If you descend down a mine shaft, you’ll notice that the temperature begins to INCREASE with depth (below about 20 m depth).

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21. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 21 Pressure and Temperature:

22. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 22 Pressure and gravity:

23. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 23 Gravity compresses interior of Sun to extreme temperatures. Problem #1: Sun is constantly losing energy. To keep it shining with a steady brightness, it would have to keep shrinking. Problem #2: Whole process would take about 10 million years. Early Ideas (cont)

24. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 24 Modern Ideas 1905: Einstein’s Theory of General Relativity Energy can be created from mass and vice-versa. All mass has an equivalent of amount of energy which is given by the formula: E=mc 2 For example: the mass in an aspirin is equivalent to a small nuclear weapon. How does the conversion take place? - subatomic (nuclear) reactions - process called fusion - example: Proton-Proton Chain

25. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 25 Review: Isotopes

26. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 26 Requires very high temperatures (greater than 10 million K)!