2. © 2010 Pearson Education, Inc. Our goals for learning:  Why was the Sun’s energy source a major mystery?  Why does the Sun shine?  What is the Sun’s structure?

3. © 2010 Pearson Education, Inc.

4. Is it on FIRE?

5. Luminosity ~ 10,000 years Chemical energy content

6. Is it on FIRE? … NO! Luminosity ~ 10,000 years Chemical energy content

7. Is it CONTRACTING? Insert TCP 6e Chapter 14 opener

8. © 2010 Pearson Education, Inc.

9. It can be powered by NUCLEAR ENERGY! (E = mc 2 ) Luminosity ~ 10 billion years Nuclear potential energy (core)

10. Gravitational equilibrium: Energy supplied by fusion maintains the pressure that balances the inward crush of gravity.

11. Weight of upper layers compresses lower layers. Insert TCP 6e Figure 14.1

12. © 2010 Pearson Education, Inc. Insert TCP 6e Figure 14.3

13. © 2010 Pearson Education, Inc. 1. The Sun appears bright orange because of the extremely hot fires that are constantly burning carbon. TRUE or FALSE 2. The sun fuses Hydrogen atoms together in its core to form Helium. TRUE or FALSE 3. Solar power output is measured in _____. a. solar unitsb. amperesc. luminosity 4. The equation discovered by Einstein that relates mass and potential energy is _____. a. PE = mg hb. E = 1/2mv^ 2c. E=mc ^ 2 5. The outermost layer of the Sun’s atmosphere which is not usually visible is the _____. a. coronab. convective zonec. core

14. http://www.pbs.org/wgbh/nova/labs/lab/sun/1/1/

15. Solar wind: A flow of charged particles from the surface of the Sun

16. Corona: Outermost layer of solar atmosphere ~1 million K

17. Chromosphere: Middle layer of solar atmosphere ~ 10 4 –10 5 K

18. Photosphere: Visible surface of Sun ~ 6000 K

19. Convection Zone: Energy transported upward by rising hot gas

20. Radiation Zone: Energy transported upward by photons

21. Core: Energy generated by nuclear fusion ~ 15 million K

22. Radius: 6.9  10 8 m (109 times Earth) Mass: 2  10 30 kg (300,000 Earths) Luminosity: 3.8  10 26 watts

24. © 2010 Pearson Education, Inc.  Why was the Sun’s energy source a major mystery?  Chemical and gravitational energy sources could not explain how the Sun could sustain its luminosity for more than about 25 million years.  Why does the Sun shine?  The Sun shines because gravitational equilibrium keeps its core hot and dense enough to release energy through nuclear fusion.

25. © 2010 Pearson Education, Inc.  What is the Sun’s structure?  From inside out, the layers are:  Core  Radiation zone  Convection zone  Photosphere  Chromosphere  Corona

26. © 2010 Pearson Education, Inc.

27. Fission Big nucleus splits into smaller pieces. (Example: nuclear power plants) Fusion Small nuclei stick together to make a bigger one. (Example: the Sun, stars)

28. © 2010 Pearson Education, Inc. Our goals for learning:  What causes solar activity?  How does solar activity affect humans?  How does solar activity vary with time?

29. © 2010 Pearson Education, Inc.

30.  Sunspots  Solar flares  Solar prominences All these phenomena are related to magnetic fields.

31. Sunspots Are cooler than other parts of the Sun’s surface (4000 K) Are regions with strong magnetic fields

32. Loops of bright gas often connect sunspot pairs.

33. Magnetic activity causes solar flares that send bursts of X rays and charged particles into space. Solar Flares classified from lowest to highest: B class C class M class X class

34. Magnetic activity also causes solar prominences that erupt high above the Sun’s surface.

35. © 2010 Pearson Education, Inc.

36. Coronal mass ejections send bursts of energetic charged particles out through the solar system.

37. Charged particles streaming from the Sun can disrupt electrical power grids and can disable communications satellites.

38. © 2010 Pearson Education, Inc.

39. The number of sunspots rises and falls in an 11-year cycle. Insert TCP 6e Figure 14.21a unannotated Insert TCP 6e Figure 14.21b unannotated

40. The calm sun on the left (Oct. 2010) is contrasted with a much more active sun on the right as it approaches solar maximum. http://youtu.be/oOXVZo7KikE

41. © 2010 Pearson Education, Inc.  What causes solar activity?  Stretching and twisting of magnetic field lines near the Sun’s surface cause solar activity.  How does solar activity affect humans?  Bursts of charged particles from the Sun can disrupt radio communication and electrical power generation and damage satellites.  How does solar activity vary with time?  Activity rises and falls with an 11-year period.