Today in Astronomy 241: the Sun

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Today in Astronomy 241 the Sun

• Todays reading Carroll and Ostlie Ch. 11, on
• The Suns interior
• The Suns atmosphere
• The Suns interior and atmosphere, according to
  StatStar and the linear stellar model
• The Sun, in visible light (top, R. Gendler) and
  neutrinos (bottom, R. Svoboda and K. Gordan, LSU,
  with Super Kamiokande). Not on the same scale,
  unfortunately.

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The Suns interior

• Central conditions, according to accurate models
  (tested with helioseismology)
• Outer 29 by radius is convective convection
  zone extends all the way to the base of the
  photosphere (this also known from
  helioseismology).

Hydrogen already substantially depleted!
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The Suns interior (continued)
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Suns interior (continued)
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Suns interior 1H, 3He, 4He abundances
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Recall the pp chain for understanding
distribution of H, He isotopes

• PP I for example (70 of pp chain reactions)

From Chaisson and McMillan, Astronomy Today
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Suns density and enclosed mass profile
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Convection condition in solar interior
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The Sun is pretty close to static
Carroll and Ostlie figure 11.2
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The StatStar Solar interior
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StatStar vs. Linear Stellar Model
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The Solar atmosphere

• Base of photosphere granulation from top of
  convection cells
• Photosphere
• T 5500 K, Frauenhofer absorption-line spectrum
  continuum opacity dominated by H-.
• Chromosphere
• increasing temperature, higher excitation
  species, emission lines.
• Corona
• very high temperatures and low density, very high
  excitation ions, forbidden emission lines.

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Problems left over from last class

• Continuing the development of the linear stellar
  modelUse the ideal gas law to get the
  temperature as a function of radius, and the
  central temperature. Note that
• Assume that radiative energy transport dominates,
  and that a Kramers law can be used for the
  opacity, to obtain an expression for dT/dr.
  Evaluate it at r R/2.
• Then produce an expression for dT/dr from the
  result of problem C, similarly evaluated at r
  R/2.

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Todays in-class problems

• Set equal the results from problems D and E, and
  obtain an expression for the luminosity generated
  within r R/2 which, because of the strong
  temperature dependence of energy generation,
  should be equal to the total luminosity of the
  star.
• Finally, use the luminosity to obtain an
  expression for the stars effective temperature,
  in terms of its mass and radius.

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Todays in-class problems (continued)

• Here are the answers, in convenient units
• A.
• B.

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Todays in-class problems (continued)

• C.D.
• E.

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Todays in-class problems (continued)

• F.
• G.