Chapter 09 Lecture
- 1. © 2007 Pearson Prentice Hall This work is protected by United States copyright laws and is provided solely for the use of instructors in teaching their courses and assessing student learning. Dissemination or sale of any part of this work (including on the World Wide Web) will destroy the integrity of the work and is not permitted. The work and materials from it should never be made available to students except by instructors using the accompanying text in their classes. All recipients of this work are expected to abide by these restrictions and to honor the intended pedagogical purposes and the needs of other instructors who rely on these materials. Lecture Outlines Chapter 9 Astronomy: A Beginner’s Guide to the Universe 5 th Edition Chaisson / McMillan
- 2. Chapter 9 The Sun
- 3. Units of Chapter 9 The Sun in Bulk The Solar Interior The Solar Atmosphere The Active Sun The Heart of the Sun
- 4. 9.1 The Sun in Bulk
- 5. 9.1 The Sun in Bulk Interior structure of the Sun: Outer layers are not to scale. The core is where nuclear fusion takes place.
- 6. 9.1 The Sun in Bulk Luminosity – total energy radiated by the Sun – can be calculated from the fraction of that energy that reaches Earth. Total luminosity is about 4 × 10 26 W – the equivalent of 10 billion 1-megaton nuclear bombs per second.
- 7. 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 :
- 8. 9.2 The Solar Interior Doppler shifts of solar spectral lines indicate a complex pattern of vibrations :
- 9. 9.2 The Solar Interior Solar density and temperature , according to the standard solar model:
- 10. 9.2 The Solar Interior Energy transport The radiation zone is relatively transparent; the cooler convection zone is opaque:
- 11. 9.2 The Solar Interior The visible top layer of the convection zone is granulated , with areas of upwelling material surrounded by areas of sinking material:
- 12. 9.3 The Solar Atmosphere Spectral analysis can tell us what elements are present, but only in the chromosphere and photosphere:
- 13. 9.3 The Solar Atmosphere 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 :
- 14. 9.3 The Solar Atmosphere Small solar storms in chromosphere emit spicules :
- 15. 9.3 The Solar Atmosphere Solar corona can be seen during eclipse if both photosphere and chromosphere are blocked:
- 16. 9.3 The Solar Atmosphere Corona is much hotter than layers below it – must have a heat source , probably electromagnetic interactions.
- 17. 9.4 The Active Sun Sunspots : appear dark because slightly cooler than surroundings:
- 18. 9.4 The Active Sun Sunspots come and go, typically in a few days. Sunspots are linked by pairs of magnetic field lines :
- 19. 9.4 The Active Sun The rotation of the Sun drags magnetic field lines around with it, causing kinks
- 20. 9.4 The Active Sun The Sun has an 11-year sunspot cycle , during which sunspot numbers rise, fall, and then rise again:
- 21. 9.4 The Active Sun 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:
- 22. 9.4 The Active Sun Areas around sunspots are active; large eruptions may occur in photosphere. Solar prominence is large sheet of ejected gas:
- 23. 9.4 The Active Sun 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:
- 24. 9.4 The Active Sun A coronal mass ejection emits charged particles that can affect the Earth:
- 25. 9.4 The Active Sun Solar wind escapes Sun mostly through coronal holes , which can be seen in X-ray images
- 26. 9.4 The Active Sun Solar corona changes along with sunspot cycle; is much larger and more irregular at sunspot peak:
- 27. 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.
- 28. 9.5 The Heart of the Sun The process that powers most stars is a three-step fusion process:
- 29. 9.5 The Heart of the Sun 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 .
- 30. 9.5 The Heart of the Sun The Sudbury neutrino observatory:
- 31. Summary of Chapter 9 Sun is held together by its own gravity and powered by nuclear fusion Outer layers of 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
- 32. Summary of Chapter 9 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