Our Star, the Sun

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Our Star, the Sun
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The Sun is the Largest Object in the Solar System

• The Sun contains more than 99.85 of the total
  mass of the solar system
• If you put all the planets in the solar system,
  they would not fill up the volume of the Sun
• 110 Earths or 10 Jupiters fit across the diameter
  of the Sun

How big is the Sun?
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An X-ray look at the Sun. http//bcs.whfreeman.c
om/universe6e/pages/bcs-main.asp?vcategorys0011
0n01000i18110.07o1800001000ns0
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The Sun goes through periods of relative activity
and inactivity
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The Suns interior has three layers(1) core(2)
radiative zone (3) convective zone
Energy generated in the core of the Sun
propagates outward through these different
layers, and finally, through the atmosphere of
the Sun. This process takes tens of thousands
of years or more.
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The Suns atmosphere also has three layers

• Photosphere - the layer we see, 5800 K
• Chromosphere - the red layer observed using a
  hydrogen filter, 10,000 K
• Corona - the incredibly thin outer atmosphere,
  1,000,000 K

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The photosphere is the visible layer of the Sun
Granulation caused by convection
http//www.whfreeman.com/universe6e - Seething
Granules around a Sun Spot
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Sunspots are the most well known feature on the
photosphere
Granulation caused by convection
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Sunspots are the most well known feature in the
photosphere. Monitoring sunspots reveals the
Suns rotation.
http//www.whfreeman.com/universe6e - the motion
of a small sun spot
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The movement of sunspots reveals that the Suns
rotation takes about
4 weeks
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The annual change in numbers of sunspots reveals
that the Sun experiences an 11-year Sun Spot cycle
Maximum number
Minimum number
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Magnetic field lines connect sunspots on the
Suns photosphere
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Solar magnetic fields also create other
atmospheric phenomena

• plages
• filaments

These features are found in the chromosphere.
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Above the photosphere, the chromosphere is
characterized by its red color from Ha
emission.
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Solar magnetic fields also create other
atmospheric phenomena

• prominences

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Solar magnetic fields also create other
atmospheric phenomena

• prominences
• solar flares

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The corona, the outermost part of the Suns
atmosphere, is characterized by its high
temperature and low density
The Sun also ejects a stream of charged particles
into space known as the solar wind
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Solar magnetic fields also create other
atmospheric phenomena

• prominences
• solar flares

• coronal mass ejections (CMEs)

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http//www.spaceweather.com/http//www.spacewea
ther.com/images2002/18mar02/cme_c3_big.gif
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The most powerful solar flare in 14 years, ..
erupted from sunspot 486 in late October of 2003.
The explosion hurled a coronal mass ejection
almost directly toward Earth, which triggered
bright auroras when it arrived on Earth.
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The Earths magnetic field is caused by movement
of material in Earths interior
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The Earths magnetic field produces a
magnetosphere that deflects and traps particles
from the solar wind protecting Earth
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Relevance of Earths protective magnetosphere

• Protects against Solar Flares - violent
  explosions on the Sun releasing large burst of
  charged particles into the solar system
• Protects against Solar Wind - dangerous stream of
  charged particles constantly coming from the Sun
• Northern Lights (Aurora Borealis)

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Northern Lights (Aurora Borealis)
As the charged particles from the Sun interact
with the magnetic field around Earth, the
particles collide with the nitrogen and oxygen
atoms in the atmosphere and excite those atoms to
emit light See Mastering Astro animation
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Aurora as seen from space