Chapter 9 The Sun

1. Chapter 9The Sun

2. Units of Chapter 9 The Sun in Bulk The Solar Interior The Solar Atmosphere The Active Sun The Heart of the Sun Summary of Chapter 9

3. 9.1 The Sun in Bulk

4. Interior structure of the Sun Outer layers are not to scale. The core is where nuclear fusion takes place.

5. Luminosity – total energy radiated by the Sun – can be calculated from the fraction of that energy that reaches Earth. Total luminosity is about 4 × 1026 W – the equivalent of 10 billion 1-megaton nuclear bombs per second.

6. 9.2 The Solar Interior Mathematical models, consistent with observation and physical principles, provide information about the Sun’s interior. In equilibrium, inward gravitational force must be balanced by outward pressure.

7. Doppler shifts of solar spectral lines indicate a complex pattern of vibrations.

8. Solar density and temperature, according to the standard solar model.

9. Energy transport: The radiation zone is relatively transparent; the cooler convection zone is opaque.

10. The visible top layer of the convection zone is granulated, with areas of upwelling material surrounded by areas of sinking material.

11. 9.3 The Solar Atmosphere Spectral analysis can tell us what elements are present, but only in the chromosphere and photosphere.

12. The cooler chromosphere is above the photosphere. Difficult to see directly, as photosphere is too bright, unless Moon covers photosphere and not chromosphere during eclipse

13. Small solar storms in chromosphere emit spicules.

14. Solar corona can be seen during eclipse if both photosphere and chromosphere are blocked.

15. Corona is much hotter than layers below it – must have a heat source, probably electromagnetic interactions.

16. 9.4 The Active Sun Sunspots appear dark because slightly cooler than surroundings.

17. Sunspots come and go, typically in a few days. Sunspots are linked by pairs of magnetic field lines.

18. The rotation of the Sun drags magnetic field lines around with it, causing kinks.

19. The Sun has an 11-year sunspot cycle, during which sunspot numbers rise, fall, and then rise again.

20. This is really a 22-year cycle, because the spots switch polarities between the northern and southern hemispheres every 11 years. Maunder minimum: few, if any, sunspots.

21. Areas around sunspots are active; large eruptions may occur in photosphere. Solar prominence is large sheet of ejected gas.

22. Solar flare is a large explosion on Sun’s surface, emitting a similar amount of energy to a prominence, but in seconds or minutes rather than days or weeks.

23. A coronal mass ejection emits charged particles that can affect the Earth.

24. Solar wind escapes Sun mostly through coronal holes, which can be seen in X-ray images.

25. Solar corona changes along with sunspot cycle; is much larger and more irregular at sunspot peak.

26. 9.5 The Heart of the Sun Nuclear fusion requires that like-charged nuclei get close enough to each other to fuse. This can happen only if the temperature is extremely high – over 10 million K.

27. The process that powers most stars is a three-step fusion process.

28. Neutrinos are emitted directly from the core of the Sun, and escape, interacting with virtually nothing. Being able to observe these neutrinos would give us a direct picture of what is happening in the core. Unfortunately, they are no more likely to interact with Earth-based detectors than they are with the Sun; the only way to spot them is to have a huge detector volume and to be able to observe single interaction events.

29. Neutrino observatories

30. The corona of the sun is only rarely visible because it is only visible during violent storms in the sun. it cannot be seen through the Earth's atmosphere. it is very faint compared to the sun's surface. it is too hot.

31. The 11 year solar cycle refers to the rate of occupance of magnetic storms on the surface of the sun. the period of rotation of the sun. the apparent motion of the sun across the sky. the nuclear reactions which occur in the center of the sun.

32. For what reason do astronomers want to observe and measure neutrinos from the sun? Neutrinos are more energetic than photons from the sun. Neutrinos are easier to detect than photons. Neutrinos give direct information about thephotosphere. Neutrinos give direct information about the sun's core. None of the above.

33. Two important characteristics of sunspots are low temperature, largemagnetic fields. high temperature, largemagnetic fields. high temperature, weak magnetic fields. low temperature, weakmagnetic fields. north and south magnetic polarities.

34. Which of these regions of the sun has the highest temperature? • Core • Photosphere • Chromosphere • Corona

35. Sunspots are caused by interaction of the sun with the planets. irregularities in the sun's magnetic field. internal faults in the sun similar to those which cause Earthquakes. no choice.

36. Differential rotation in the sun makes the equator move faster than higher latitudes. the higher latitudes move faster than the equator. the magnetic field rotate faster than the surface. none of these.

37. Combining two nuclei together requires high temperatures to remove the electrons which surround the nuclei. overcome the electric repulsion of the nuclei. make sure the nuclei thoroughly mix when they collide. force the nuclei to expand.

38. Which of the following statements about the energy generating process in our sun is true? It can be duplicated efficiently on Earth with our present technology. Mass is converted to energy. Hydrogen becomes helium in one step. We have detected many more neutrinos from the process than we expected to find.

39. Which of the following is true in the proton-proton chain? Protons are fused to produce deuterium or heavy hydrogen. Protons are split to form neutrons and positrons. Protons produce helium directly. Protons decay into energy and neutrinos.

40. The main nuclear reactions that keep our sun shining begin with which building blocks? • Three carbon nuclei. • Two electrons. • Two hydrogen nuclei. • A deuteron and a positron.

41. The heaviest element that can be created in normal nucleosynthesis is • iron. • helium. • uranium. • carbon. • bagelium.

42. Summary of Chapter 9 • The Sun is held together by its own gravity and powered by nuclear fusion. • Outer layers of the Sun: photosphere, chromosphere, corona. The corona is very hot. • Mathematical models and helioseismology give us a picture of the interior of the Sun. • Sunspots occur in regions of high magnetic fields; darker spots are cooler.

43. Summary of Chapter 9, cont. • Nuclear fusion converts hydrogen to helium, releasing energy. • Solar neutrinos come directly from the solar core, although observations have told us more about neutrinos than about the Sun.