Sun – chapter 16

1. Sun – chapter 16 Composition, Energy source, Structure, “normal life” changes

2. Goals & Outcomes • Explain how electromagnetic radiation and astronomical instruments are used to reveal the properties of stars and galaxies. • Diagram the process of nuclear fusion. • Learn about some problems astronomers and astrophysicists are trying to solve, and understand the methods scientists are using to try to solve these problems. • Develop a sense of what scientists know about the overall universe, its constituents, and our location • Diagram and explain radiative transport in the Sun. Explain the causes of surface features on the Sun.

3. Major Sun facts • What’s a star? • _______________________ • ________, so it must ___________________.Must protect your body if in space! • Which ___________________? • ____________________________________ • Other: O=1%, C=0.4%, Fe=0.14%, N=0.1%, Si, Mg, Ne, S 0.040.1%. • How do we know these numbers?

4. Sun’s Age • Easy to measure: ___________________ • Can figure out ______________ • __________________ tell us age must be____________________________ • _________________ tell us ___________ • What can make the Sun shine so bright for so long?

5. Sun The picture shown to the right is taken using the Hydrogen 3  2 transition (red colored, called H-alpha

6. Power Sources and how long Sun could shine See common misconception__________ • This is discussed on page _________. • ____________________________________ • ____________________________________ • ____________________________________ • Until 1920, ___ idea _____________________. • _____________________________________ • _______________. (Do humans use _______?) • ______________________________________ • (For more details, see figure 14.7 – not on test) • Every sec: ________tons ___ into ________tons __. • Can do this for a total of _______________ years • How old is Sun. How much time left? • Review: what’s H atom made of? He atom?

7. Why is fusion difficult for people & Sun? • What is nuclear fusion? What’s in the nucleus? • Why would they be ____________________? • Fig 14.6, top • What must happen to ___________________? • _____________ “turns on” when ___________ • Fig 14.6, bottom • Why ________________________________? • How do you overcome this? • Where are conditions right? • ____________________________________ water • Humans use more energy than fusion releases, with current technology. Wait 30 years!

8. At what temperature does helium fuse with another helium? • Also at 15 million K • Less than 15 million K • More than 15 million K

9. Calif. Elementary School Science Standards for nuclear processes • From California Science Standards, high school • Students know protons and neutrons in the nucleus are held together by nuclear forces that overcome the electromagnetic repulsion between the protons • Students know the energy release per gram of material is much larger in nuclear fusion or fission reactions than in chemical reactions. The change in mass (calculated by E = mc2 ) is small but significant in nuclear reactions. • Students know the Sun is a typical star and is powered by nuclear reactions, primarily the fusion of hydrogen to form helium.

10. Structure & evolution of the Sun • Start with a clicker question.

11. Star lives – a constant struggleFigure _________, page _______ • Gravity tries to ____________________ • Shrinking wins until … • Some source of _____________________ • What is the Sun? (What is any star?) • Big sphere of _________________________. • ____________________________________ _____________________________. • Think of an example of balls of gas in your everyday life. • What do you do to _________________________ (i.e. _________________________)?

12. Gravity & Pressure imbalance(pp. __________) Figure 14.8 • If _________________ than gas pressure, what happens? • Gas ___________ and becomes _____ when it _________________. • Fusion in the core will _________. Star _____ • If ______________________ than gravity, what happens? • Gas ___________ and becomes _____ when it _____________. • Fusion in the core will _________. Star _____

13. Review question: Does the mass of the Sun change over its lifetime? • Yes • No

14. Review question: How does the mass of the Sun change over its lifetime? • Not at all • A little bit, but not noticeable • The Sun’s mass changes noticeably

15. Sun’s structure – radiation transport • See figure _______, page ______. • ___________________________ • ______________________ K • ______________ – where energy carried by ______ • _______________ – energy carried by ____________ • ________________ – ________________________ • ______ – ______________________ – see pic above • How could we see this? • _________________ comes off the Sun. • _______________________________________. • Causes ____________________ (aurora borealis/australis). • Affect atmospheres, magnetism

16. Radiation & Convection Zones • Core is hot – thermal emitter • __________________________________ • _____________________________________________ • _____________________________________. Figure ___________ • “_________________ photons” • Takes __________________________ to “walk” from core  outside • ___________________________________ • Outer layers are ________________, stuff gets _________ • Photons get “_______________” • ______________. _______________. _________________ • Movement is visible through ECC scopes! • See figure ____________ • ___________________________ • __________________________. Outside temp: _______ K. • Quick review question: how long does it take light to get here once it leaves the Sun?

17. Evil scientist magically turns off fusion. Would you notice after 6 minutes? • Yes • No

18. Evil scientist magically turns off fusion. Would you notice after 10 minutes? • Yes • No

19. The amount of Helium in the Sun is: • Increasing • Decreasing • Staying the same

20. What’s happening to the number of particles in the Sun’s core? • Increasing • Decreasing • Staying the same

21. Slow evolution of the Sun • What happens to core gas pressure as a result of ________________________________? • What happens to the core? It _____ and _____. • That causes what? • Balance restored! • What happens to fusion rate? • What happens to the Sun’s luminosity?

22. Studying Sun’s interior • Helio__________________________ • See figure 14.11 • ____________________ tell us about insides • Strongest clues about interior of the Sun • Figure 14.12 shows results

23. Solar Neutrinos • ________________(turning proton into neutron). • 3% of Sun’s energy in neutrino form. 97% light. • ________________________________________ • _________________________________________ • _________________they interact with stuff • ___________. See figure 14.14 page 506 • 60 billion/cm2/sec. New million ton detectors “see” ___ neutrinos per day. [New versions: looking for dark matter!] • We saw 1/3 to ___________________from fusion • HUGE puzzle • Solution (May 2001): neutrinos _______________ • ____________________weren’t detectable in past.

24. Another neutrino detector • Japanese - Super Kamiokande • filled with 50,000 tons of water • 13,000 light detectors(seen on wall)

25. Link to Earth - spots • What are the spots? • Hotter or colder than the rest of the photosphere? • Like ___________ ______________, they’re _________ _______________

26. ______________________ • ____________________: • _____________________ • ______________________ • ___________________ (probably) • _________ Rotation: figure _____

27. Solar _____________ • Sunspots go through _________________ – few spots to many back to few. • 2007 “Solar _______________________” • When is the next “Solar maximum” • Cycle isn’t a perfect clock • Some cycles stronger than others • Figures 14.22 & 14.23 • There might be a link to _______________ / _____. But __________________________.

28. Summary • We know the Sun fuses based on its age • Fusion energy source & productS • Composition (general) • Why fusion is difficult (repulsion, strong force) • Gravity vs. pressure. How currently balanced? • Different “layers” of Sun, a little about each • Neutrinos – what, where, problem? • Magnetic fields • Solar Cycle – time, observable results • A PUZZLE: north pole is warmer than south pole by 80,000K all the time. (Does not flip when magnetic field does.) Stay tuned.