What Is The Sun Made Of

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What Is The Sun Made Of?
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Absorption bands in the Solar Spectrum

• 1802 Wollaston sees dark bands
• 1814 Fraunhofer records many lines and labels
  with letters these become known as Fraunhofer
  lines
• 1859 Kirchoff realizes the significance of dark
  lines as absorption lines coming from elements in
  the gas

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Internal Structure

• Core Temp 270,000,000 F
• Where nuclear fusion occurs
• Location of energy production in the Sun
• Radiation Zone Temp 12600000 F 3600000 F
• Energy travels by radiation
• (photons) inner 2/3 of sun
• Convective Zone Temp 3600000 F outer 1/3 of
  sun
• Energy travels by convection(bubbles of heated
  material)
• Photosphere Temp 9950 F
• Chromosphere Temp 9950 F

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Energy Production

• Hydrogen fuses in the core of the sun.
• Fusion means 4H lt-gt 1He,
• Emc2 Energy is produced by this process because
  of the difference in binding energies between H
  and He
• Conservation of Energy means energy is released
  each time a reaction occurs

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Outer layers Photosphere

• Photosphere visible layer of the sun!
• Location of observed Blackbody Spectrum
• Continuum tells us the Temperature

T 9950 F
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Effective Temperature

• Blackbody curve from last week Hot dense gas
  emits continuous emission. The wavelength of peak
  intensity determines the temperature

Intensity vs wavelength
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Outer layers Chromosphere

• Chromosphere observed in the H-alpha line
• Looks red!!
• Top layers hotter than photosphere
• Lower layers cooler than photosphere
• Cool gas in front of a Blackbody creates
  absorption lines...

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Outer layers Corona

• Corona has a temperature much higher than lower
  layers(4,000,000 deg F), and much lower density
• Not fully understood even now - magnetic fields
  are most probably involved...
• Solar Flare clip

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Spectral Typing

• Stars of different spectral types have different
  absorption lines in their spectra
• Different lines because different temperatures
• Different temperatures because different masses

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Elements in the Sun
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Sunspots

• Sunspots are cooler places on the Photosphere
  where magnetic field lines break through the
  surface
• Cooler spots look darker compared to their
  surroundings
• The sun has an 11 year cycle from few sunspots to
  many. Currently we are moving towards a minimum

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Today's lab

• A few notes to guide the discussion of the
  questions
• Q1 what is the response of the video detector to
  color?
• Q5 video camera insensitive to these wavelengths,
  but photographic emulsions very sensitive to
  them, so much easier to see
• Q6 think about Kirkoff's laws...
• Q8 what do we breathe...? lines from Earth are
  called telluric lines
• Q9 Heavy elements like Iron (Fe) need to be very
  very hot to turn into a gas and thus emit or
  absorb light at particular wavelengths. Even
  hotter temps lead to the loss of electrons
  ionization...the corona has Fe XIV (Iron ionized
  13 times!!)