1. Unit 9: The Sun Mr. Ross Brown Brooklyn School for Law and Technology

2. In this unit we will learn about: The structure the Sun, from core to solar wind Why the Sun must continually generate heat and where that heat goes The process of nuclear fusion Einstein’s equation of the conversion of mass to energy, E=mc 2 How magnetic fields and gas in the Sun interact How solar activity affects the Earth, through both individual and long-term events

3. What are the properties of our Sun? 22 February 2016 Do now: What are the main gases that comprise the Sun? In what percentages?

4. What are the properties of our Sun? 150 million km from the Earth – 93 million miles – 1 AU

5. What are the properties of our Sun? 71% Hydrogen 27% Helium 2% heavier elements (Carbon, Oxygen, etc.) Core is 15,000,000°K, or 27,000,000°F

6. Converting Kelvin to Celsius to Fahrenheit Kelvin: absolute zero. No molecular motion Celsius: Kelvin + 273. Water freezes at 273°K, or 0°C, and boils at 373°K or 100°C Fahrenheit: to convert from Celsius: 9/5C+32 and add 21

7. What are the properties of our Sun? Solar Interior – Photosphere: the visible layer of the Sun – Density is about that of our atmosphere – Temperature about 6,000°K – As we move into the Sun, heat and density rise

8. How does energy move within the Sun? We know that heat always moves from hot to cold Near the core, radiative zone. Gas is very dense, so photons travel outward very slowly

9. How does energy move within the Sun? Convection Zone: just below photosphere Granulations: bright regions surrounded by darker regions, bubbles of hot gas rising to surface

10. What are the parts of the solar atmosphere? Lower density just above the Photosphere Chromosphere: lower atmosphere. Spicules: long jets of hot gas shooting out About 4500°K near to photosphere up to 50,000°K

11. What are the properties of our Sun? Corona: Sun’s outer atmosphere, beyond photosphere. Temperature reaches 1 million K. Only seen during eclipse when Moon blocks the Sun.

12. Homework #16 23 February 2016 What visible evidence do we have that the Sun has a convection zone? Explain.

13. How does the Sun maintain its shape? 24 February 2016 Do now: How does a balloon maintain its shape?

14. How does the Sun maintain its shape? Inward force on the Sun due to its _________ Outward force due to motion of its atoms, which creates outward pressure We call this hydrostatic equilibrium, and it must remain perfect Gravity

15. How does the Sun maintain its shape? Pressure in a gas comes from collisions between atoms and molecules – What increases the number/ frequency of collisions? – Increases in density or temperature

16. How does the Sun maintain its shape? Ideal Gas Law – Pressure=Density x Temperature x Constant – Sun Density: 160 g/cm 3 – Sun Temperature (core): 15 million K

17. How does the Sun maintain its shape? Energy produced by the Sun escapes and warms the Solar System – How does the Sun stay warm enough to not collapse? Sub-atomic energy!

18. How does the Sun generate energy? 25 February 2016 Do now: How is nuclear fusion different from combustion (burning fuel)?

19. How does the Sun generate energy? E=mc 2 Energy can be produced from mass E=energy that can be produced by M=mass times the C 2 =square of the speed of light – 3*10 8 meters/second – 1.86*10 5 miles/second HOW??????

20. How does the Sun generate energy? Nuclear Fusion – Conversion of hydrogen atoms into helium atoms – 2 or more atomic nuclei bond into a single, heavier one

21. How does the Sun generate energy? Nuclear Fusion! – Possible due to extreme high heat – Hydrogen is + charge, should repel each other – Smashed together at high speeds and held together by the STRONG FORCE – This process is the Proton-Proton Chain

22. How does the Sun generate energy? Isotopes of Hydrogen and Helium

23. How does the Sun generate energy? Proton-Proton Chain

24. How does the Sun generate energy? We lose some mass but we gain energy – How many H went in? – How many H came out?

25. Homework #16, part 2 25 February 2016 Briefly (but fully) explain the “solar neutrino problem.”

26. How do we detect activity from the Sun’s core? Solar neutrinos – Produced as Hydrogen is converted to Helium – Amount of neutrinos tells us how active the Sun is

27. How do we detect activity from the Sun’s core? Solar neutrino detectors – Miles underground, protected, filled with water

28. How do we detect activity from the Sun’s core? Solar neutrino puzzle – Early detectors didn’t find the suspected number – Scientists applied the scientific method – Revised detectors now work much better

29. How do we detect activity from the Sun’s core? Solar seismology – Waves pass through the Sun, providing information – Different gases have different densities Hydrogen to helium ratio

30. How do we detect activity from the Sun’s core? Solar Magnetic Fields – Similar to Earth, rotation of material within core – Result in solar storms and phenomena

31. What is the impact of the Sun’s magnetic field? Sunspots – Cooler than surrounding parts of photosphere

32. How do we detect activity from the Sun’s core? Solar prominences – Huge plumes of gas – Cooler than gas around them, thus lower pressure

33. How do we detect activity from the Sun’s core? Solar flares – Produced when sunspots erupt with hot gases – Large flares may lead to more auroras and disruption of Earth’s communications systems

34. How do we detect activity from the Sun’s core? Solar wind – Gases hot enough to escape the Sun’s gravity – Mainly hydrogen and helium – Travel very fast and very far, to the boundaries of our solar system

35. How does the Sun’s Solar Cycle affect Earth’s climate? 1 March 2016 We will start today by finishing yesterday’s notes, but right now…. Do now: How do you think fluctuations in the Sun’s magnetic field could affect Earth’s climate?

36. How does the Sun’s Solar Cycle affect Earth’s climate? Solar Cycle: change in observed number of sunspots, year upon year

37. How does the Sun’s Solar Cycle affect Earth’s climate? The Sun is gas rotating. Wider at equator, so gas there rotates faster. We call this differential rotation.

38. How does the Sun’s Solar Cycle affect Earth’s climate? Kinks in the Sun’s magnetic field produce sunspots Polarity switches after each solar cycle

39. How does the Sun’s Solar Cycle affect Earth’s climate? Magnetic field heats the corona Corona drives solar wind Solar wind affects Earth’s upper atmosphere, and may affect the Jet Stream

40. How does the Sun’s Solar Cycle affect Earth’s climate? Periods of less sunspot activity correspond to periods of colder winters – Maunder minimum, or little ice age

41. How does the Sun’s Solar Cycle affect Earth’s climate? Is there a link between sunspot activity and ocean surface temperatures?