24.3 The Sun

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24.3 The Sun
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Hot facts

• Sun ball of GAS (not fire!)
• 99.9 of all matter of our Solar System is in the
  sun
• The sun is an average star
• It is a Main-Sequence star (well learn about
  later)
• One of 100 billion stars that make up the Milky
  Way Galaxy
• The only star whose surface we can study

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The Active Sun

• Not all parts of the sun rotate at the same speed
• Equator rotates once in 25 days (faster)
• Poles rotate once every 33 days (slower)
• Conclusion the sun is gaseous

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Structure of the Sun

• Made of gas, no sharp boundaries exist between
  its internal layers
• The sun is divided into four parts
• Solar Interior
• Photosphere (visible surface)
• Chromosphere (layer of its atmosphere)
• Corona (layer of its atmosphere)

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Photosphere

• Meaning photos light, sphere ball
• Visible surface of the sun
• Radiates energy to space
• Has a grainy texture made of bright markings
  called granules produced by convection.
• Temp averages approx 10,000ºF
• 90 of the suns surface atoms are hydrogen

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Chromosphere

• The first layer of the solar atmosphere found
  directly above the photosphere.
• - chroma color sphere
• Relatively thin, hot layer of incandescent gases
  a few thousand miles thick.
• Its top contains numerous spicules, which are
  narrow jets of rising material.
• Chromosphere is observable during a total solar
  eclipse

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Chromosphere
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Corona

• Meaning corona crown
• Outermost layer of the solar atmosphere.
• Visible only during an eclipse when the bright
  photosphere is covered
• The temp at the top of the corona exceeds 2
  million degrees F.

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• Solar wind - stream of protons and electrons
  erupted at high speed from the solar corona
• Interacts with bodies of the solar system
• Earths magnetic field prevents
• solar wind from reaching our surface

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Sun Spots

• Dark spots on the sun, they are cool in
  contrast to the surrounding photosphere.
• Sunspots appear dark because of their
  temperature, which is about 2000 degrees less
  than that of the surrounding solar surface.
• Some history During early nineteenth century it
  was believed a tiny planet named Vulcan orbited
  between Mercury and the Sun. It turned out the
  planet Vulcan was actually a series of sun spots!
  oops

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Sun Spots
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Prominences

• Meaning prominere to jut out
• Huge cloudlike structures consisting of
  chromospheric gases.
• Appear as arches
• May seem to hang motionless for days or may be
  explosive
• Prominences are ionized gases trapped by
  magnetic fields that extend from regions of
  intense solar activity.

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Prominences
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Solar Flares

• Brief outbursts that normally last about an
  hour and appear as a sudden brightening of the
  region above a sunspot cluster.
• Solar flares release enormous amounts of energy,
  much of it in the form of ultraviolet, radio, and
  X-ray radiation.
• Auroras (Northern or Southern Lights)
• result of solar flare
• bright displays of light caused by solar
  radiation interacting with Earths upper
  atmosphere near the poles

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Nuclear Fusion

• The way that the sun produces energy.
• In this reaction four hydrogen nuclei combine to
  form one helium nucleus, releasing a tremendous
  amount of energy.

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Nuclear Fusion

• The sun has enough fuel to exist in its present
  stable state for 10 billion years.
• The sun is already 4.5 billion years old, so it
  is middle-aged
• When the sun does come to its final stages, it
  will expand and engulf the first 4 planets

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