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The Sun

The Sun. Internal structure of the Sun Nuclear fusion Protons, neutrons, electrons, neutrinos Fusion reactions E = mc 2 Transport of energy in the sun How do we know? Reading chapter 18.1-18.5. The Sun. The Sun. Internal Structure of the Sun.

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The Sun

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  1. The Sun • Internal structure of the Sun • Nuclear fusion • Protons, neutrons, electrons, neutrinos • Fusion reactions • E = mc2 • Transport of energy in the sun • How do we know? • Reading chapter 18.1-18.5

  2. The Sun

  3. The Sun

  4. Internal Structure of the Sun Core temperature 15,600,000 K, density 150 water Surface temperature 5800 K, average density 1.4 water

  5. Nuclear burning

  6. Nuclear burning • What do all those funny symbols mean? Elementary particles • Protons (orange) – found in nuclei, positive charge • Neutrons (blue) – found in nuclei, no charge • Electrons (e-) – orbit nuclei, negative charge • Photons (g) – particles of light (gamma-rays) • Positrons (b+) – anti-matter electrons, positive charge (e+ in book) • Neutrinos (n) – `ghost particles’, no charge, can easily pass through normal matter

  7. Convert proton to neutron • To convert a proton to a neutron • A positron (b+) and a neutrino (n) must be produced and released

  8. Make nuclei out of protons and neutrons 1H = normal hydrogen nucleus = proton 2H = deuterium hydrogen nucleus (unstable) = proton plus neutron (in heavy water) 3He = light helium nucleus (unstable( = two protons plus one neutron 4He = normal helium nucleus = two protons plus two neutrons

  9. Nuclear burning

  10. Nuclear burning • OK, so you turn 4 hydrogen nuclei into on helium nucleus, but why do you get energy out? • One helium nucleus has less mass than 4 hydrogen nuclei by about 0.1%, and E = mc2

  11. E = mc2 • Einstein showed that mass and energy are equivalent (c = speed of light) • Mass can be converted to energy, and • Energy can be converted to mass • The Sun is powered by the conversion of mass into energy • So are nuclear reactors and nuclear bombs

  12. Internal Structure of the Sun

  13. Gas in the Sun is in hydrostatic equilibrium

  14. Fish in water are in hydrostatic equilibrium

  15. Transport of energy through the radiative zone It takes about 200,000 years for photons made in the core to make it through the radiative zone

  16. Convective zone

  17. Do the following transport energy by convection or radiation? • A gas oven • A microwave • A heat lamp • An electric radiator

  18. How do we know? Core temperature 15,600,000 K, density 150 water Surface temperature 5800 K, average density 1.4 water

  19. How do we know?

  20. We see the neutrinos Neutrinos don’t bounce around like photons, come straight out. Neutrinos are only produced in nuclear reactions. Ray Davis shared the 2002 Nobel prize in Physics for originally detecting neutrinos from the Sun.

  21. We see oscillations on the surface of the Sun

  22. Helioseismology is a way to probe the Sun’s interior using the Sun’s own vibrations. • The surface of the Sun vibrates up and down in oscillations which can go deep through the Sun. • We can observe these oscillations from Earth by looking at the Doppler shifts of different pieces of the Sun.

  23. Waves inside the Sun The pattern of waves on the surface is determined by the conditions deep inside the Sun.

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