The Sun: closeup of a spectral class G main sequence star

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The Sun close-up of a spectral class G main
sequence star
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Illustration of Kirchoffs 1st Law
A hot object emits more radiation at all
wavelengths than A cooler object (Figure 7-6)
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Structure of a Sunspot
Note granulation
Sunspots are regions of very strong magnetic
field (2000 Gauss)
Demo
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Sunspots represent tubes of magnetic field lines
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This causes sunspots to often occur in pairs,
with opposite magnetic poles
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Sunspots and magnetism
http//sohowww.nascom.nasa.gov/gallery/Movies/
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Solar magnetic fields reach far out into space
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The 11 Year Solar Cycle

• The Sun has a heartbeat its properties change
  on a period of 11 years

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Latest data on this sunspot cycle
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The Sunspot Cycle has been going on for a long
time
Observations show cycle persisting, but turning
off from 1650 to 1730 (Maunder Minimum)
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The Structure of the Solar Atmosphere

• Photosphere
• Chromosphere
• Corona
• Temperature increases as you go up
• Outermost layer flows out into space to form the
  Solar Wind

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The solar corona
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The solar corona
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The Solar Wind

• A wind past the Earth at 400 km/sec
• The Sun is melting away
• Density 19 orders of magnitude less than
  atmosphere
• A medium for solar events
• May have sandblasted the early atmosphere of
  Mars

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Explosions on the Sun Solar Flares and Coronal
Mass Ejections
The occurrence of flares and CMEs is enhanced
around The time of solar maximum
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The Lesson for Other Stars

• Do they also have sunspots, sunspot cycles, etc?
• How does all this (magnetic fields, solar wind,
  rotation) relate to the age of a star?