4 Layers of the Sun. CORE : center, where fusion occurs

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Thomasina Randall
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1 4 Layers of the Sun CORE : center, where fusion occurs RADIATION LAYER: energy transfer by radiation (like energy coming from a light bulb or heat lamp which you can feel across the room) CONVECTION LAYER: energy transfer by convection (like air from your furnace being blown through your house) PHOTOSPHERE: what we see 1

2 Layers of the Sun Mostly Hydrogen with about 25% Helium. Small amounts of heavier elements Gas described by Temperature, Pressure, and Density with P= kdt (mostly)(k= a constant) Larger temperature near Radius = 0 Inner radius is a PLASMA - gas where all atoms are ionized. T >100,000 degrees K and so free electrons H (48) He (4) electron(56) 2

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4 Equilibrium Temperature of the Sun is constant for any given radius. It doesn t change as heat flows out Gravitational Force pulling in BALANCES the gas pressure (Electric force) pushing out At center : highest gravitational pressure gives the highest temperature 4

Convection Zone T = 6,000 100,000 K Radiation Zone T = 100,000 5,000,000 K Temp is highest in the

5 Convection Zone T = 6, ,000 K Radiation Zone T = 100,000 5,000,000 K Temp is highest in the core where nuclear fusion occurs heat flows outward to surface, then radiated as light to (say) Earth 5

6 Core - Center of Sun High temperature ~15,000,000 degrees K high density ~ 100 g/cm 3 where fusion occurs H He and heat flows out source of neutrinos 6

7 Core - changes with time As heavier, Helium produced by fusion reaction tends to float to the center. For now, He isn t burning and there is a mini-core of (mostly) He with reduced fusion being built up Red=H green=he 7

8 Radiation Layer temperature 100,000 to 5,000,000 degrees (plasma) no fusion electrons are not in atoms very, very opaque Energy transferred by absorption and reradiation of light photon photon photon electron electron 8

9 Convection Layer temperature 6,000 to 100,000 degrees no fusion electrons in atoms less opaque Energy transferred through convection. Movement of gas to/from surface ( hot air rises) 9

10 Convection and Radiation layers differ on how heat is transferred 10

11 Photosphere Sun gas cloud no true surface Light we see comes from a 200 km fairly transparent region called the photosphere which is the outermost layer temperature 4,500-6,000. The 6000 degree part is the top of the convective layer photosphere Convection region 11

Photosphere Absorption Lines temperature photosphere 4,500-6,000 cooler than convection region dark line absorption spectrum from light traveling through

12 Photosphere Absorption Lines temperature photosphere 4,500-6,000 cooler than convection region dark line absorption spectrum from light traveling through absorption region Absorption lines give atoms present in Sun (where Helium was first discovered), and from Doppler shift velocity of gas cells moving up/down at surface 12

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14 Outer Atmosphere of Sun Surface of the Sun hot, turbulent with electric/magnetic storms which throw out energetic particles CHROMOSPHERE low density, high T glows red (H atom emission) seen in eclipse CORONA even lower density and higher T (over 1,000,000 degrees) and higher velocity SOLAR WIND protons escaping Sun s gravity so largest velocity. Can interact in Earth s atmosphere 14

Sunspots Intense magnetic fields which inhibit convection currents to the surface appear darker as at lower temperature Solar storms/flares often associated with sunspots Had been observed prior to

15 Sunspots Intense magnetic fields which inhibit convection currents to the surface appear darker as at lower temperature Solar storms/flares often associated with sunspots Had been observed prior to Galileo s time (and without telescopes) Galileo gets credit as he had best explanation Sunspot activity varies with time. 11 year cycle plus variation over hundreds (thousands) of years change in Solar energy output 15

16 Outer Atmosphere Can see Corona/Chromospere during eclipses. Interactions of solar wind with Earth s magnetic field and atmosphere causes Aurora Borealis. Parker Solar Probe launched in 2018 will study 16

Magnetic fields pull charged particles toward Earth s

17 Aurora Borealis Northern Lights seen at high latitudes as magnetic fields are lower in the atmosphere. Magnetic fields pull charged particles toward Earth s surface at the poles. rarely seen in DeKalb. Photos are from Alaska and Maine 17

Solar Storms Large eruptions from Sun s surface are called flares or storms Will increase flow of charged particles to Earth, increase Northern

18 Solar Storms Large eruptions from Sun s surface are called flares or storms Will increase flow of charged particles to Earth, increase Northern Lights, and have (some) radiation impact (plane flights, on space station, radio signals) Large one in January 2012, September Atmosphere protects us 18

19 Extra Slides 19

20 Test 1 Possible short answer questions Motion of Sun, stars, planets through sky vs seasons Galileo s astronomical observations Kepler s Laws of planetary motion Newton s Laws of motion apply to Kepler s (mostly F=ma) how light is produced (accelerated charge) plus discrete vs. continuous nuclear reactions in the Sun : p-p cycle Layers in the Sun 4 forces with examples Web page has an example test with typical multiple choice questions 20

Proton-proton cycle 3 steps PHYS 162 1

Proton-proton cycle 3 steps PHYS 162 1 4 Layers of the Sun CORE : center, where fusion occurs RADIATION: energy transfer by radiation CONVECTION: energy transfer by convection PHOTOSPHERE: what we see