A peek into the sun

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A peek into the sun
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Suns structure is layered gravity versus
radiation

• Nuclear burning core
• proton-proton cycle 1H ? 4He g (26.72) MeV
• 150 times denser than water
• 16 million K at center, so matter is a dense
  plasma of protons (34) and other nucleii, and
  electrons, in active nuclear burn
• Radiative zone
• g absorbed, re-emitted MANY TIMES as they
  diffuse out through this high-opacity zone
• ? 170,000 years on average to get out!
• only 8 million K or less burning stops
• Convection zone
• rising/falling hot gas/plasma make surfacecell
  structures
• surface temperature is 5800 K 71 hydrogen

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Mass into Energy E mc2

• Chemical (wood, TNT, Heathbar)
• ?107 J/kg, or 1 eV/molecule
• 1 kg of fuel (107 J) heats 50 lbs water from 0C
  to 100 C
• Nuclear (fission, fusion)
• ?10 MeV/molecule, or 1014 J/kg
• Actually more like 1012 J/kg in practice
• .01 g of mass will do the same job!!
• in a given nuclear reaction, a tiny amount of
  matter is lost for a proton, mc2 931 MeV, so
  10 Mev is 1/90 of a protons mass

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Fusion Fission

• two lighter nuclei combine a nucleus
  splits in two
• the hydrogen bomb the atomic
  bomb

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The Suns Source of Power

• Combustion? Fuel content c 1 x 107 J/kg (e.g.
  paper) M 2 x 1030 kg P 4 x 1026 W implies
  lifetime Mc/P 5 x 1010 s 1600 years!
  Biblical time scale but we know better
• Meteor Collisions (matter infall)? Escape
  velocity
• v 600 km/s, so with kinetic energy K (1/2)
  mv2 in one year need mass 2P(1 year)/v2 7 x
  1022 kg about 1/100 earths mass which is 6 x
  1024 kg every year Not obviously unworkable but
  no good!!
• Gravitational Contraction? Actually a partial
  explanation. Kelvin-Helmholtz time (to shrink to
  current size at current P value) is not so far
  off!!
• Nuclear Fusion? Hans Bethes proton-proton chain
  is a series of nuclear reactions that take H to He

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The Nuclear Furnace

• Basic Fuel HYDROGEN (proton) 1H
• 1H 1H gt 2H b n
• (2 protons form deuterium, positron, neutrino)
• 2. b b - gt g energy!!
• (positron annihilates electron, yielding gamma)
• 3. 2H 1H gt 3He g energy!!
• 4. 3He 3He gt 4He 1H 1H
• Summary 6 1H gt 4He 2 1H 26.72 Mev

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The neutrino (little neutral particle) problem

• Three kinds electron, tau, muon Electron
  version produced in COPIOUS quantities by sun
• Pass through everything (almost)!!
• We dont see enough PROBLEM!!
• May or may not have a mass!!
• Super-Kamiokande sees terrestrial ones too

Note little scientist in boat
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Fig.17.06
The limb of the sun is darker
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Fig.17.10
Granulation on the surface of the sun

• looking at the tops of convective cells
• bright areas are rising hot gas
• dark areas are cooled sinking gas

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Chromosphere and Corona the atmosphere of the sun

• only visible during total solar eclipses
• chromosphere is cool, Balmer-line dominated
• corona is hot, highly ionized material

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The sun in visible and in ultraviolet

• coronal structure is highly variable
• note prominences and solar flares
• flares are huge explosions of magnetic field

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The 22-year sunspot cycle magnetic lines tangle