1. 24.3 The Sun Explain the structure of the Sun.
OBJECTIVES
Explain the structure of the Sun.
Describe the physical features on the surface of the Sun.
Explain how the Sun produces energy

2. 24.3 The Sun VOCABULARY Photosphere Chromsphere Corona Solar wind
Sunspot
Prominence
Solar flare
Aurora
Nuclear fusion

3. The Sun can be divided into four parts:
(1) visible surface, or photosphere
two atmospheric layers:
(2) chromosphere
(3) corona
(4) solar interior (and core)

4.  Photosphere (Light Sphere)
• Releases most of the energy we receive on Earth
• Its a layer of incandescent gas less than 500 kilometers thick
• Visible Surface of Sun!
• Its temperature averages approximately 6000 K (10,000ºF).

5.  Chromosphere (Color sphere)
• The first layer of the solar atmosphere found directly above the photosphere. (Orange-Red Layer)
• A hot layer of incandescent gases a few thousand kilometers thick.
• Its top contains numerous narrow jets of rising material.

6.  Corona • Outer most layer of the solar atmosphere.
• The temperature at the top of the corona exceeds 1 million K.
• Solar wind is a stream of protons and electrons ejected at high speed from the solar corona.

7. 24.3 The Sun
 Corona
A coronal mass ejections can be larger thatn the sun itself!

8. They increase then decrease over an 11 year cycle
The Active Sun
• Sunspots appear dark because of their temperature, which is about 1500 K less than that of the surrounding solar surface.
 Sunspots
• A dark spot on the sun that is cool in contrast to the surrounding photosphere.
They increase then decrease over an 11 year cycle

9. The Active Sun  Prominences
• Huge cloudlike structures consisting of chromospheric gases.
• Prominences are ionized gases trapped by magnetic fields that extend from regions of intense solar activity.

10. The Active Sun  Solar Flares
• Brief outbursts that appear as a sudden brightening of the region above a sunspot cluster.
• They release enormous amounts of energy, mostly in the form of UV, radio, and X-ray radiation.

12. Aurora Borealis
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The result of solar flares, bright displays of light caused by solar radiation interacting with the upper atmosphere in the region of the poles
Video

13. The interior cannot be observed
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14. The Solar Interior  Nuclear Fusion
• This reaction converts hydrogen nuclei into the nucleus of a helium atom. This is the way that the sun produces energy.
• During nuclear fusion matter is converted to energy. E=mc2
• It is thought that the sun can exist in its present stable state for 10 billion years. As the sun is already 4.5 billion years old, it is “middle-aged.”

15. Nuclear Fusion
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16. Radiation and Convection
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