1. The Sun The Sun Link to opening video

2. Stellar Fusion Where does the sun get its energy? The process of nuclear fusion in which particles in the nucleus of the atom combine to form larger nuclei. This larger nucleus has a slightly smaller mass than the nuclei that combined to make it. The missing mass has been converted to energy. The sun is made mostly of hydrogen which has been fusing to helium for about 5 billion years, and will continue to do so for about 5 billion more. Fusion link

3. Stellar Composition So, the sun is mostly hydrogen, with a lot of helium, with very small amounts of other material. Where did this other material come from? In the 1 st part of the introductory video they told us that it came from the explosion of earlier stars. We discussed this when we learned about other stars. ElementPercentage Comp. Hydrogen73.5 Helium24.8 Carbon0.33 Nitrogen0.12 Oxygen0.79 all other elements0.46

4. E = mc 2 The amount of energy created in this process can be calculated by the famous equation above. What does it mean? Matter is changed into energy during fusion The amount of energy created when you change matter to energy is equal to the mass of the matter converted times the speed of light constant c squared (a very large number), so E = mc 2 This is a lot of energy for a small amount of matter, and billions of reactions occur every second in stars, producing great amounts of energygreat amounts of energy

5. Energy from matter Whenever matter is destroyed, energy is created. For example, when you light a match, the combustible material contains potential energy as matter. During the reaction this material changes mostly to other matter, but a little changes to energy, in the form of heat and light. This is just like the food you eat which is stored solar energy. This is chemically changed to energy to fuel your body. Chemical reactions like these create energy - but only small amounts compared to the amount created from nuclear reactions - like fusion in stars.

6. Fusion vs fission Both fusion and fission can create energy from matter, as long as the process gives out more energy than it takes to make it occur Fission is the process of splitting a nucleus In natural fission, the energy required to split the nucleus is less than what is obtained when it splits. Again, in fission, there would be less mass after the reaction since matter is transformed into energy. Thus the law of conservation of energy and matter is followed. How can both fusion and fission generate energy by transforming matter to energy? This involves what is called binding energy. We discussed this briefly when we discussed the evolution of stars.

7. The Sun, a complicated place The Sun, a complicated place The Sun, a complicated place The Sun, a complicated place

8. The sun’s layers Core – where fusion takes place Radiation zone Convection zone Photosphere – the “surface” of the sun Chromosphere – the red color layer Corona – the sun’s crown A closer look at the sun link Energy is created by fusion reactions in the core. This energy migrates to the surface.

9. The Sun in 4 Wavelengths Continuum 30.4 nm Soft x-rays H α We can learn a lot about the sun by observing it with different instruments that can “look” at different wavelengths of light.

10. The Sun in 4 more Wavelengths Link from classzone Link from classzone Link from classzone 17.1 nm 393.4 nm (Ca K) 1038 nm 28.4 nm

11. Different wavelengths show different solar layers Links: H sunspots 80 K He 1.6 M Iron UV1.6 M Iron UV and Flaring region UV iron 2 M X rays Magnetic and corona split Spots to UV

12. Different heights… Different wavelengths…

13. Composite of eight images taken at different wavelengths

14. Active regions in different wavelengths Trace video link

15. Spectra – Bar Code of the Sun & Stars A hot object emits light with many wavelengths and a certain shape If this light passes through a gas, the atoms and molecules of the gas will be absorbed at specific wavelengths. The details of these dark absorption lines provide information on the gas. There is more on this in the spectra presentation

16. The Visible Solar Spectrum

17. Solar Atmospheric Chemical Composition

18. The McMath-Pierce Solar Telescope

19. Observing in the McMath-Pierce with Dr. Steven Howell, astronomer Ms Starkins

20. The Earth’s Magnetosphere

21. Magnetic Fields Both the sun and earth have magnetic fields. Do you remember what causes magnetic fields? Moving charged particles generate magnetic and electric fields. Electromagnetic radiation consists of moving electric & magnetic fields. We know that swirling liquid iron in the outer core causes the earth’s dynamic magnetic field. What causes the sun’s magnetic field? The hydrogen atoms in the sun are actually ions (charged nuclei), in which the electrons are removed from the atoms because of the high temperature of the sun. As these ions move, they generate electric and magnetic fields – these moving fields are the light we see, as well as the other electromagnetic radiation (like x-rays, UV, etc.) generated by the sun

22. Galileo Galileo was among the 1 st (if not the 1 st ) to use the newly invented telescope and observe spots on the rotating sun. We have Galileo’s drawings of his sunspot observations. This Link animates them in orderLink These showed the rotation of the sun. Since the sun is gaseous, the rotation varies from poles to equator. The rotation is faster at the equator. This causes shearing which twists the magnetic field lines and produces small local magnetic fields.

23. Both magnetic fields The earth’s magnetic field The earth’s magnetic field is distorted by charged particles from the solar wind and flare activity. Twisted magnetic field lines Twisted magnetic field lines created by sun’s rotation cause sunspots and solar flare activity.

24. A magnetogram A magnetic field picture of the sun showing the localized magnetic fields.

25. Polarity of fields Magnets, as you know, have two poles, a North and a South pole The magnetic field flows between these two poles Notice the field lines of the Earth’s magnetic field on the next slide You should be able to see these loops that go between the north and south pole The field deflects charged particles and the loops trap charged particles

26. Magnetic Fields,Sunspots & Magnetic Loops Magnetic Loops  trapped, hot gases …as seen in X-ray Magnetic Fields  lines that connect north and south polarities Fly through the loops

27. SUNSPOTS

28. Remember that heat migrates upward from the core through the convection and radiation zones. Sunspots occur where magnetic fields prevent rising of heated material. Therefore this spot is cooler than the surrounding sun. A sunspot has a temperature of about 1500 degrees less than the surrounding photosphere.

29. Sunspot link Although these sunspots look dark, they would be brighter than a full moon if viewed separately from the sun. Backed by the hotter sun, they appear black.

30. Material flows around sunspots

31. Notice that sunspots are commonly as large as, or larger than, the whole earth.

32. Magnetic fields cause interesting structures on the sun

33. Like Prominences Prominence link

34. And they can erupt in solar flares link link

35. Movie Storms on the Sun

36. And eject material towards Earth CME to earth link

37. Which impacts technology

38. And causes auroras Aurora video At both poles usually Sometimes far south with major solar activity Sometimes far south with major solar activity Classzone picturespictures

39. Images of flares, CME’s Link Link 2 Link 3Link 3 combined to see sun and corona A coronagraph uses a telescope with a piece blocking the sun, so that the corona can be observed at any time. In effect, it makes an artificial eclipse.

40. The Solar Wind Of course there is always some material streaming out through holes in the corona. This steady flow of particles is called the solar wind

41. Magnetic fields rise and fall in cycles. The number of sunspots shows this. It increases to a maximum number about every 11 years. 11 year sunspot/activity cycle 11 year sunspot/activity cycle It is actually a 22 year cycle. For the first 11 years the fields point in one direction. Then for the next 11 years they go the opposite direction. This is similar to the changes in magnetic field directions on the earth, but happens more quickly and is apparently more consistent. Of course, this is only based on what we have observed over a relatively short period of time.

42. The 11-year activity cycle

43. Link showing cycle changesLink showing cycle changes 91 to 01 Link showing comparison from 96 to 99

44. Effects of Solar cycles Does this affect the earth? There is evidence to show that long periods of low sunspot activity correspond to cooler periods on the earth. For example, the Maunder Minimum from 1645 – 1716 had very low sunspot activity and corresponded with a cold episode called the “Little Ice Age.” Classzone.com sunspot activity And worksheetworksheet

45. What does the sun look like today? Where are we in the solar cycle? If you were carefully looking at the graphs and pictures before, you probably know. Let’s see if you are right. SOHO website (If this isn’t working, the Space Weather site below can also help you.) Space Weather site for solar storms, aurora forec.asts and other items Space Weather

46. What is This? sun videos\transit_label_large.mov Cool images from STEREO websiteSTEREO website

47. How did the sun begin and how will it end? Link 1 – formation of sun Link 2 – death of sun 1 Link 3 – death of sun 2