The Solar System

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The Solar System

• Section 2 The Sun

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Guide For Reading

• How does the sun get its energy?
• What are the layers of the suns atmosphere?
• What are some features of the suns surface?

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The Suns Interior
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Nuclear Fusion

• Hydrogen atoms join together to form helium
• An extremely high temperature and pressure are
  needed
• The suns core is 15 million degrees Celcius

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Core

• The center of the sun
• The temperature reaches about 15 million degrees
  Celsius, high enough for nuclear fusion to occur

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Checkpoint Where in the sun does nuclear fusion
occur?

• Nuclear fusion occurs in the suns core.

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Guide For Reading How does the sun get its
energy?

• The suns energy comes from nuclear fusion
• Nuclear fusion The process by which hydrogen
  atoms join together to form helium, releasing
  energy.

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The Suns Atmosphere
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Layers Of the suns Atmosphere

• Photosphere The inner layer of the suns
  atmosphere. The Greek word photo means light.
• Chromosphere The middle layer of the suns
  atmosphere. The Greek word chromo means color.
• Corona The outer layer of the suns atmosphere,
  which looks like a halo around the sun. The
  Latin word corona means crown.

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Figure 7 Inferring Why is it easiest to
photograph the suns outer layers during a solar
eclipse?

• During a solar eclipse, the suns bright inner
  layers are blocked, making the outer layers
  easier to see

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Solar Wind

• A stream of electrically charged particles
  produced by the suns corona
• Near the poles where the particles enter Earths
  atmosphere, where they hit gas molecules and
  cause them to glow
• Auroras (Northern Lights)

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Auroras (Northern Lights)
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Checkpoint During what event could you see the
suns corona?

• You can see the suns corona during a solar
  eclipse.

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Guide For Reading What are the layers of the
suns atmosphere?

• The suns atmosphere has three layers the
  photosphere, the chromosphere, and corona.

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Features on the Sun
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Sunspots

• Areas of gas on the sun that are cooler than the
  gases around them

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Prominences

• Reddish loop of gas that protrudes from the suns
  surface, linking sunspots

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Solar Flares

• An explosion of hydrogen gas from the suns
  surface that occurs when loops between sunspots
  suddenly connect

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Figure 9 Relating Cause Effect How can solar
flares affect communications on Earth?

• Solar flares increase the solar wind in the
  corona, which can cause magnetic storms in
  Earths upper atmosphere
• These storms often disrupt radio, telephone, and
  television signals

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Guide For Reading What are some features of the
suns surface?

• Features on or above the suns surface include
  sunspots, prominences, and solar flares.
• Sunspots ? Prominences ? Solar Flares ? Magnetic
  Storms

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