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A peek into the sun

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Chromosphere and Corona: the atmosphere of the sun. only visible during ... chromosphere is cool, Balmer-line dominated. corona is hot, highly ionized material ... – PowerPoint PPT presentation

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Title: A peek into the sun


1
A peek into the sun
2
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

3
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

4
Fusion Fission
  • two lighter nuclei combine a nucleus
    splits in two
  • the hydrogen bomb the atomic
    bomb

5
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

6
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

7
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
8
Fig.17.06
The limb of the sun is darker
9
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

10
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

11
The sun in visible and in ultraviolet
  • coronal structure is highly variable
  • note prominences and solar flares
  • flares are huge explosions of magnetic field

12
The 22-year sunspot cycle magnetic lines tangle
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