The Sun

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The Sun
2
Components of the Sun

• Core
• Radiative zone
• Convective zone
• Atmosphere
• Photosphere
• Chromosphere
• Corona
• Solar wind (mass loss)

3
Solar Power

• Suns glow fueled by Nuclear Fusion
• Fusion is process by which lighter atoms undergo
  collisions that spawn heavier atoms and a
  release of energy for radiation
• Fission, on the other hand, is when a heavy atom
  breaks up to yield a lighter atom plus energy

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Proton-Proton Chain

• p-p chain converts 41H 14He
• (so 4 bare protons combine to make a helium
  nucleus with 2ps and 2ns)
• Also get photons and neutrinos in this process
• Neutrinos are (nearly) massless particles
  traveling near light speeds and interacting only
  weakly with matter

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The Chain
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Solar Neutrinos

• Neutrinos are elementary particles moving near
  light speed, but which interact only weakly with
  matter.
• They are important because they can come from
  nuclear reactions and emerge directly from the
  core of the Sun.
• Raymond Davis arranged the first neutrino
  experiment. He discovered a neutrino problem,
  but this seems to be resolved today.

A modern neutrino experiment, Super-Kamiokande
run by Japan
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Share Question

• Tremendous pressure is created at the Sun's
  center due to its own gravity. What keeps it
  from collapsing?
• a) neutrinos and other particles generated by
  nuclear fusion
• b) a hard inner core
• c) thermal (gas) pressure generated by
  nuclear fusion
• d) thermal (gas) pressure left over from the
  formation of the Sun

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Solar Atmosphere

• Photosphere the layer that we see in visible
  light
• Chromosphere tenuous, somewhat hotter layer
  above photosphere
• Corona extended region of million degree gas
  above chromosphere

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Emergence of Light from the Core
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Perspectives of the Sun
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A Solar Eclipse
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The Transition Region
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Solar Activity

• Sunspots cool blemishes that come and go on an
  11 year cycle
• During cycle, spots initially appear at high
  latitudes and thereafter at progressively lower
  lats.
• Prominences extended columns of gas that trace
  out magnetic loops (can rise to 50,000 km above
  photosphere)
• Flares explosive and energetic events involving
  hot gas of up to 40 million K

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Sunspots
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Solar Granulation - Convective Cells
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Spicules
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Prominences
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Prominence Movie
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Solar Cycle in X-rays
X-ray emission from the solar corona, taken every
120 days, from 1991 (left) to 1995 (going right)
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Solar Cycle in Extreme UV
Images from the SOHO satellite
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Sun-Earth Connection
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Solar Wind Movie
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CME Movie 1
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CME Movie 2
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Magnetic Loops at the Sun
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Butterfly Diagram
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Sunspot Number
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Understanding The Solar Cycle
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(No Transcript)
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Solar Cycle and the Earths Climate
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The Solar Wind

• 1951, Biermann discovered solar wind by
  considering comet tails
• Speed near earth around 400 km/s travel
  time across 1 AU is 4 days
• Provides injection of material resulting in
  aurorae
• Combination of wind and magnetic field have
  caused a spin down of Suns rotation

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Solar Wind Mass Flux
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Space Weather
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The Resonating Sun
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Solar Sailing

• To make G gt 1 requires a material with
• (A/m) gt 1300 m2/kg (equivalent to 36m x 36m)
• For 1 kg of sail, and G 2, Fnet 0.006 N

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Long-Term Changes in the Sun
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Temperature-Luminosity States
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Solar Endpoints Planetary Nebulae