The Sun

1. The Sun

2. Take-Away Points • The Sun is an ordinary middle-sized star • The sun creates energy by nuclear fusion in its core • The visible surface of the Sun is called the photosphere • A thin cool layer, the chromosphere, allows us to determine what the sun is made of • A very thin but very hot outer layer is called the corona • Convection in the sun is revealed by granulation • Features on the sun include sunspots, prominences, spicules and faculae • Disturbances on the sun affect electrical and electronic equipment on Earth

3. The Sun • Distance: 150 million km (93 million miles) = 8.3 light minutes • Diameter: 1.4 million km (870,000 miles) = 109 x Earth • Mass = 330,000 x Earth • Bulk density = 1.4 gm/cc • Surface temperature = 5800 K • Rotation: 25 days at equator, 34 at poles 1. The Sun is an ordinary middle-sized star

4. The Solar Interior • Ideal Gas Law: • Pressure x Volume is proportional to Temperature • Pressure = weight of overlying material 2. The sun creates energy by nuclear fusion in its core

5. Interior of the Sun

6. Structure of the Sun • Core: 0-20% of radius. Energy produced by nuclear fusion • Radiative Zone: 20-70% of radius: Energy travels as thermal radiation • Tachocline: Boundary of Radiative Zone: Exterior slips over interior • Convective Zone: Outer 30% of Sun: Energy moves by convection 2. The sun creates energy by nuclear fusion in its core

7. Core of the Sun • Energy output: 90 billion megatons/second • Energy output = 6 microwatts/kg – less than a candle • Human body outputs 1.2 W/kg – 200,000 times greater • By volume: Core of Sun = 0.9 W/m3; Human body = 1200 W/m3. • Trying to duplicate sun’s energy output not practical on Earth; We try to use other fusion processes • Energy takes 10,000 – 100,000 years to reach surface 2. The sun creates energy by nuclear fusion in its core

8. Solar Energy • 4 H  He • 4H = 4 x 1.00794 = 4.03176 • He = 4.002602 • Difference = 0.029158 = 0.7% = 1/140 • Converted to energy via E=mc2 • Once you get over being freaked out by Einstein, this is middle school math 2. The sun creates energy by nuclear fusion in its core

9. Solar Energy • E=mc2 • m = kg • c = m/sec = 300,000,000 • E = joules (one Watt = 1 J/sec) • Sun’s energy output = 3.8 x 1026 W • How much mass is that per second? • m = E/c2 = 3.8 x 1026/(300,000,000)2 = 4 billion kg/sec 2. The sun creates energy by nuclear fusion in its core

10. Solar Energy • Sun converts 4 billion kg of matter to energy every second • Matter conversion = 1/140 of original mass • Sun converts 560 billion kg of H to He (5.6 x 1011 kg) every second • Mass of Sun: 2 x 1030 kg • 2 x 1030 kg/ 5.6 x 1011 kg/sec = 3.6 x 1018 sec = 114 billion years 2. The sun creates energy by nuclear fusion in its core

12. The Sun We Can See • Photosphere: The Visible Disk • More transparent than air • We can see a couple of hundred kilometers deep • Chromosphere • Thin cooler atmosphere • How we know what stars are made of • Corona • Very thin but very hot • Why so hot is a mystery

13. Layers Of The Sun

14. Features On The Sun • Limb Darkening • Granulation • Sunspots • Faculae • Plages: hot clouds in the Chromosphere • Flares • Prominences

15. Surface of the Sun

16. Supergranulation

17. Supergranulation

18. Sunspots and Faculae

19. Sunspots, Faculae, Limb Darkening

20. Solar Spicules

21. Solar Prominence

22. Solar Corona