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The Sun

The Sun. Abundance of Elements in the Sun. Element % by Number % by Mass Hydrogen 92.0 73.4 Helium 7.8 25.0 Carbon 0.02 0.20 Nitrogen 0.008 0.09 Oxygen 0.06 0.8 Neon 0.01 0.16 Magnesium 0.003 0.06. Moon's Orbit. Visible sphere of the Sun. Relative sizes.

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The Sun

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  1. The Sun

  2. Abundance of Elements in the Sun Element % by Number % by Mass Hydrogen 92.0 73.4 Helium 7.8 25.0 Carbon 0.02 0.20 Nitrogen 0.008 0.09 Oxygen 0.06 0.8 Neon 0.01 0.16 Magnesium 0.003 0.06

  3. Moon's Orbit Visible sphere of the Sun Relative sizes Earth

  4. Structure of the Sun

  5. What Makes the Sun to Shine? • Chemical • Would only provide the necessary energy for 3000 years • Gravitational Contraction • Proposed by Helmholtz and Kelvin - would power the Sun for a few hundred million years • By the early 1900’s geologists showed that the Earth is billions of years old.

  6. Nuclear Energy

  7. Fundamental Forces • Strong Nuclear • Holds the nucleus of the atom together • Electromagnetic • Responsible for all chemical reactions • Weak Nuclear • Governs radioactive decay • Gravity

  8. Proton-proton chain e+ 2H Step 1 1H + 1H —> 2H + e+ + neutrino n Step 2 2H + 1H —> 3He + photon 3He photon 1H 4He Step 3 3He + 3He—> 4He +1H + 1H +photon photon 1H

  9. Hydrogen Fusion • Net result • 4H --> He + e+ + n + energy • Four protons are 0.7% more massive than one He E = mc2

  10. Neutrino Telescope Ar Ar Argon Atom Cosmic Rays 1.6 km 100,000 gal. tank Gold Mine C2Cl4

  11. Solar Neutrino Problem

  12. Animation

  13. Energy Transport • Conduction: the transfer of heat in a solid by collisions between atoms and/or molecules. • Not applicable in stars • Radiation: the transfer of energy by electromagnetic waves. Inside the Sun and most stars, radiation is the principal means of heat transport. • Convection: the transfer of heat in a gas or liquid by means of the motion of the material.

  14. McMath-Pierce Solar Telescope

  15. Photosphere Big Bear Solar Observatory October 21, 2009

  16. The Sharp Limb Transparent here • Limit of resolution is one arcsec • 700 km at 1 AU • Density falls very quickly in photosphere Opaque here

  17. Limb Darkening • Same 700 km penetration depth • Viewed at disk center, light originates deeper • Temperature falls with height in photosphere

  18. Temperature of Photosphere Photosphere

  19. Solar Spectrum

  20. Granulation • Typically 1000 km across • Bright center, dark edge • Center moving out, edges moving in The Movie

  21. Granulation Convection Cool Hot Hot

  22. Chromosphere • Observing strategies • During total eclipses

  23. Chromosphere • Using spectroheliograph Ha

  24. Chromosphere Supergranulation

  25. Chromosphere CaII

  26. Spicules Movie

  27. The Corona The quiet corona The active corona

  28. X-ray emission The Movie

  29. Average particle velocity Velocity Escape Velocity Distance from photosphere Solar Wind

  30. The Corona is Hot • The Corona is hot! • X-ray emission • Lines of highly ionized iron • FeX, FeXIV, FeXV • Requires T  2,000,000 K • Coronal holes are the source of the Solar Wind

  31. End of Section

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