1. Chapter 9 Our Star, the Sun

2. What do you think? What is the surface of the Sun like? Does the Sun rotate? What makes the Sun shine?

4. Outer Layers of the Sun’s Atmosphere Photosphere - the 5800 K layer we see Chromosphere - the red layer observed using a hydrogen filter at a million degrees Corona - the incredibly thin outer atmosphere at millions of degrees

5. The photosphere is the visible layer of the Sun Granulation caused by convection

6. Sunspots are the most well known feature on the photosphere

7. Above the photosphere, the chromosphere is characterized by spikes of gas called spicules

8. Supergranuals surrounded by spicules

9. The corona ejects some of its mass into space as the solar wind

10. Monitoring sunspots reveals the solar cycle and the Sun’s rotation

11. The daily movement of sunspots reveals that the Sun’s rotation takes about 4 weeks

12. The annual change in numbers of sunspots reveals that the Sun experiences an 11-year solar cycle Maximum number Minimum number

13. The cyclical change in the latitude of sunspots also reveals that the Sun experiences an 11-year solar cycle

14. The Sun’s magnetic fields create sunspots Zeeman effect - spectral lines split in regions of high magnetic fields

15. Magnetic field lines connect sunspots on the Sun’s photosphere

16. Babcock’s magnetic dynamo is one possible explanation of the sunspot cycle where magnetic field lines become complexly entangled after many solar rotations

17. Solar magnetic fields also create other atmospheric phenomena plages filaments

18. Solar magnetic fields also create other atmospheric phenomena plages filaments prominences

19. Solar magnetic fields also create other atmospheric phenomena plages filaments prominences solar flares

20. Solar magnetic fields also create other atmospheric phenomena plages filaments prominences solar flares coronal holes

21. Solar magnetic fields also create other atmospheric phenomena plages filaments prominences solar flares coronal holes coronal mass ejections (CMEs)

22. Thermonuclear reactions in the core of the Sun produce its energy At extremely high temperatures and pressures, 4 Hydrogen atoms can combine to make 1 Helium atom and release energy in the process according to E = mc 2 4H  He + energy H YDROGEN F USION

23. Solar models describe how energy escapes from the Sun’s core through the: (1) core, (2) radiative zone, and the (3) convective zone

25. Helioseismology is the study of solar vibrations in order to determine the detailed interior structure of the Sun

26. Mystery of the Missing Neutrinos Current models of the solar interior predict that 10 38 neutrinos are released every second Current neutrino detectors on Earth watch for collisions between perchloroethylene cleaning fluid (C 2 Cl 4 ) and neutrinos which produces radioactive argon. Only 1/3 of the expected neutrinos from the Sun are being detected Astronomers do not know why this occurs

27. What did you think? What is the surface of the Sun like? The photosphere is composed of hot, churning gases. There is no solid or liquid region in the Sun. Does the Sun rotate? The Sun’s surface rotates differentially. The rate varies between once every 25 and once every 35 days. What makes the Sun shine? Thermonuclear fusion at the Sun’s core is the source of the Sun’s energy.

28. Self-Check 1: Name the three layers of the solar atmosphere and describe and the relative temperatures and densities in each. 2: Describe flares, spicules, granules, prominences, and sunspots and identify the layer in the solar atmosphere in which is found. 3: Indicate what is observed in helioseismology and explain its value in investigating the Sun. 4: Explain the nuclear fusion process that is the principal energy source in the solar interior and describe the physical conditions required for this process to proceed effectively. 5: List and describe the two primary mechanisms for energy transport in stellar interiors and indicate in which regions of the solar interior, if any, each is dominant.