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Chapter 9 The Main Sequence

Chapter 9 The Main Sequence. Four fundamental forces of nature. Hydrostatic equilibrium: negative feedback loop. If core T drops, fusion rate drops, core contracts heats up. If core heats up, fusion rate rises core expands cools down.

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Chapter 9 The Main Sequence

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  1. Chapter 9 The Main Sequence

  2. Four fundamental forces of nature

  3. Hydrostatic equilibrium: negative feedback loop • If core T drops, • fusion rate drops, • core contracts • heats up • If core heats up, • fusion rate rises • core expands • cools down

  4. Main sequence stars are modeled as concentric spherical shells in hydrostatic equilibrium Mass element dm Constant density  Inward force = outward force

  5. Binding energy holds a nucleus together:BE = total mass of each individual nucleon - mass of nucleus

  6. The Coulomb barrier: 1 in 1085 particles has the energy to cross it

  7. Wave function Probability distribution

  8. Quantum tunneling

  9. Gamow Peak: energy region where the reaction is more likely to take place Can’t tunnel through Coulomb barrier Few particles

  10. Another view of Gamow peak

  11. One of 3 branches of proton-proton chain

  12. CNO cycle:C, N O atoms act as catalysts

  13. T-dependence of pp chain and CNO cycle

  14. Solar neutrino problem: Early searches for solar neutrinos only found ~1/3 the expected number of neutrinos

  15. Solar neutrino problem: Early searches for solar neutrinos only found ~1/3 the expected number of neutrinos Neutrinos apparently can change form. According to nuclear physics theory, this means they must have mass! “flavor oscillation”

  16. Super-Kamiokande in Japan. • 1 km underground (in a mine) • 11,000 light-detectors in/around a pool of water • Neutrino can (rarely) interact with a proton • A particle is produced that moves faster than the speed of light in water • Causes an optical “sonic boom”

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