1. Chapter 29

2. Sec 1 Structure of the sun People believed the sun’s energy came from fire They believed the sun burned some type of fuel to produce energy < 100 yrs ago, scientists discovered the source of sun’s energy

3. The Sun’s Energy Sun is too bright to look at with naked eye Astronomers use special filters and specialized scientific instruments Composition of the sun Spectrograph is used to break sun’s light into spectrum Studying the spectrum, scientists determine amts of elements present in the stars atmosphere

4. Composition of sun cont. Hydrogen- about 75% Helium – about 24% Total amount of these two gases 99% of the sun’s mass Trace amounts of other elements

5. Nuclear Fusion The process of combining nuclei of small atoms to form more-massive nuclei. Fusion releases huge amts of energy Nuclei of H atoms primary fuel for the sun’s fusion H 1 p+ 1 e- Inside the sun e- are stripped from the P+ by sun’ intense heat

6. 3 steps to Nuclear fusion Figure 2 page 756 Step1 --- 2 H nuclei (P+) collide and fuse + charge of one of the P+ is neutralized as that particle emits a particle called a positron This results in the P+ becoming a N 0 which changes the original 2 P+ into a Proton/Neutron pair Step 2 --- another P+ combines with this proton/neutron pair which produces a nucleus of 2 P+ and 1 N 0

7. Step 3 --- 2 nuclei make up the 2 P+ and 1 N 0 collide and fuse As this fusion happens 2 p+ are released The remaining 2 P+ and 2 N 0 fuse together and form a Helium (He) nucleus During EACH step of the reactions ENERGY is RELEASED

8. The Final Product One final product of fusion of H is always a He nucleus He nucleus 0.7% < mass than H nuclei that combined to form it and the lost mass is converted to ENERGY during the series of fusion reactions that form He

9. Mass Changing Into Energy Fusion > sun’s energy Mass lost during fusion > energy 1905 Albert Einstein proposed that a small amt of matter yields a LARGE amt of energy Nuclear fusion unknown at the time Nucleus of atom not yet discovered Einstein’s Theory of Relativity included E = mc 2 Where E is energy produced m is mass and c 2 is speed of light http://fuse.pha.jhu.edu/outreach/kit1/lightspeed.h tmlhttp://fuse.pha.jhu.edu/outreach/kit1/lightspeed.h tml

10. Einstein’s equation helped astronomers to explain the huge quantities of energy produced by the sun Sun changes 600 million tons of H into He every second This amt of H is small compared to the total amt of H in the sun

11. Copy figure 4 page 758 The Sun’s interior Scientists can’t see directly so models are used Motion of sun’s surface aids in studying its interior *The core – 25% of total diameter of 1,380,000 km Temp of core 15,000,000 0 C and is ionized gas No liquid or solid exists at this temp

12. *The Radiative Zone – The zone surrounding the core Temp ranges from 2,000,000 to 7,000,000 0 C energy in this zone moves outward in the form of electromagnetic waves, or radiation *The convection Zone – surrounds the radioactive zone Temp 2,000,000 0 C Energy produced in the core moves through this zone through convection (the transfer of energy by moving matter)

13. Convection zone cont. Hot gases carry energy to the surface Hot gases move outward, expand, and lose energy Cooling gases denser and sink to the bottom of the conv. Zone where they are heated again by the radiative zone and rise again Thus, Energy is transferred to the sun’s surface as gases rise and sink

14. The Sun’s Atmosphere has 3 layers 1.The photosphere – “sphere of light” – innermost layer made of gases that have risen form the convection zone – temp 6,000 0 C – most energy given off here in the form of visible light – layers are transparent so the visible light is seen from Earth – sunspots – cool areas/dark spots – 3,800 0 C – page 759 fig 5

15. 2. The Chromosphere – “color sphere” – thin layer of gases – glows with reddish light typical of H – temp range 4,00 – 50,000 0 C – gases in chromosphere move away from the photosphere 3. The sun’s Outer Parts – corona (“crown”) is the outermost layer – huge region of gas - temp above 1,000,000 0 C Not very dense – magnetic field prevents most atomic parts from escaping into space – e- & ions can escape –produce solar winds which flows out from the sun to the rest of the solar system

16. Sec. 2 Solar Activity Sunspots – cool dark areas of gas within the photosphere – strong magnetic fields on regions of the sun lead to sunspots because CONVECTION slows and ENERGY decreases The sunspot cycle – lasts 11 years – sunspots showed astronomers that the sun rotates

17. Solar Ejections Events in which the sun emits atomic particles Include prominences, solar flares, coronal mass ejections Solar – activity- cycle is caused by the changing solar magnetic field

18. Prominences A disturbance in the sun’s atmosphere caused by the magnetic fields - Great clouds of glowing gases that form huge arches that reach high above the sun’s surface – commonly associated with the chromosphere

19. Solar Flares Most violent solar disturbance – a sudden eruption of electrically charged particles (e- and p+) – trigger for this is unknown – they release energy stored in the strong magnetic fields – temp of flares reach 20,000,000 0 C

20. Coronal Mass Ejections Some flare particles escape into space. – these particles increase the strength of solar winds – some particles escape into space as CME – parts of the corona thrown off the sun – read more on page 763(how sun affects day to day life on Earth)

21. Auroras On Earth, spectacular effect of the interaction between the solar wind and Earth’s magnetosphere is the bands of light called auroras -Usually seen close to the magnetic poles – usually occur after solar flares occur – Northern lights and Southern lights