Goals

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(No Transcript)
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• Goals
• Describe the internal structure of the Sun
• Describe the surface detail and how it probes
  the interior
• Describe how the Suns magnetic field effects
  solar activity
• Explain the energy source of the Sun Nuclear
  fusion
• Explain how understanding the Sun has helped
  define Physics

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The Sun is our nearest star. The next closest
star is 300,000 times further away (Alpha
Centauri). Alpha Centauri is 4.3 light years
away and our Sun is 8 light minutes away. Our
Sun is absolutely average in every aspect
(size,mass, brightness, etc.) compared to the
other stars in our galaxy. The Sun is 300,000
times more massive than the Earth and its radius
is more than 100 times the size of Earths.
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The Sun is a mass of incandescent gas. It has no
solid surface. The surface, called the
photosphere is simply where the gas becomes
optically thick and we cant see through
it. Since the surface becomes thick in just
0.1 percent of the radius, the Sun appears to
have a sharp edge.
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There are three well defined regions which are
defined by the way energy is transported within
them. In the core is the site of continuous
nuclear reactions which convert mass into energy
according to EMC2 . (100 billion, 1-megaton
nuclear bombs/sec). The radiation zone is where
the Sun appears transparent to the energy and
photons move freely.
The convection zone is where hot material rises
to the surface like a pot of boiling water.
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The Sun is stable because of hydrostatic
equilibrium
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The Sun, being made up of gasses, wiggles,
shakes, and rings like a giant bowel of Jell-O.
The way in which it rings tells us about its
interior just like seismic waves tell us about
the interior of the Sun just like seismic waves
tell us about the interior of the Earth. This
field of study is called helioseismology
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Scientists modeling the Sun calculate that the
temperature at the core is near 15,000,000 K
while we measure the black body radiation curve
at the surface and get 5,800 K. As the
convection cells near the surface and radiate
their energy away, we see their effect as
granulation.
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The Solar Atmosphere
A Spectrum of our Sun shows many dark absorption
lines, indicating the presence, in the lower
solar atmosphere, of 67 elements in various
stages of ionization.
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Solar Chromosphere
Solar Surface
Corona Holes in X-rays
Solar Corona
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Sun Spots
Sunspots are actually cool spots on the Sun which
look dark because they give off less light than
the surroundings
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Sunspots occur in pairs, one being a north pole
the other being the south. They are produced
when knots of magnetic fields surface from below
caused by their wrapping due to differential
rotation.
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Because of the coupling between matter and
magnetic fields, the differential rotation and
convection twist the magnetic field lines.
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It takes about 11 years for the magnetic field
lines to get all wrapped around, and then the
poles of the sun actually flip. What was north
is now south. This causes the 11 year sunspot
cycle.
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Hot gasses which are boiling off the Sun tend to
follow the magnetic field lines, producing loops,
prominences, and flares. Those that escape make
the Solar wind.
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Energy from the Sun
It wasnt till early this century when Albert
(Al) Einstein produced the Special Theory of
Relativity that we understood how the Sun gets
its energy. The famous equation E MC2 shows
how matter can be converted to energy (and vise
versa)
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The Sun (and all stars) through a process called
the proton-proton cycle converts 4 H nuclei into
He and giving up energy. This is the same
process used in a Hydrogen bomb. A Hydrogen
bomb is just a piece of the core of the Sun
released on Earth for a brief amount of time.
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The only major unknown concerning the energy
production of the Sun is the amount of neutrinos
(30-50 less) being produced. Several
underground chambers have been built to detect
neutrinos to help solve this problem.