1. Youtube:
Secrets of a
Dynamic Sun
The Sun – Our Star
Our sun is considered an “average” star and is one of the 100 BILLION stars that make up the Milky Way galaxy.
But by no MEANS does that make our star insignificant! Everything - from the fossil fuels we burn to the foods we eat – is ultimately derived from solar energy.

2. General Properties Average star 109 times Earth’s diameter
333,000 times Earth’s mass
Consists entirely of gas (av. density = 1.4 g/cm3)
Central temperature = 15 million 0K (27 million 0F)
Surface temperature = K (10 thousand 0F)
Ultra-violet image

3. Structure of the Sun
Because the sun is made of gas, no sharp boundaries exist between its various layers. Keeping this in mind, we can divide the sun into four parts:
the solar interior (core)
the visible surface, or photosphere
two atmospheric layers:
the chromosphere
the corona.

4. Solar Interior

5. The Layers of the Solar Atmosphere
X-ray
Visible
Sun Spot Regions
Photosphere
Corona
Chromosphere
Coronal activity, seen in visible light

6. Solar Interior: Nuclear Fusion
• Nuclear fusion is the way that the sun produces energy. This reaction converts 4 hydrogen nuclei into the nucleus of 1helium atom, releasing a tremendous amount of energy.
• During nuclear fusion, energy is released because some matter is actually converted to energy.

7. Nuclear Fusion Makes no sense without caption in book Nuclear Fusion
Creating
New Elements
Makes no sense without caption in book

8. The Photosphere
Radiates energy back into space, the part we see of the sun!
Depth ≈ 500 km
Temperature ≈ 5800 oK (10,000 oF)
10 Day
Solar Animation

9. Obtained 24.10.2012 at 7:26 am EST with HMI instrument on board SDO spacecraft

10. Energy Transport in the Photosphere
Energy generated in the sun’s center must be transported outward. In the photosphere, this happens through Convection.
This convection creates a grainy texture called granules that are the size of Texas!
Bubbles last for
≈ 10 – 20 min.
Bubbles of hot gas rising up
Cool gas sinking down
≈ 1000 km

11. Granulation
Granules
… is the visible consequence of convection

12. Sun Spots X-ray Visible
They’re magnetism is 1000x’s stronger than the magnetic field of the sun!
They occur in the photosphere and they were originally discovered by Galileo in * It is a dark spot on the sun that is cool in contrast to the surrounding photosphere. *Sunspots are cooler because of the Sun’s magnetic field.

13. Cooler regions of the photosphere (T ≈ 4240 K).
Sun Spots
Cooler regions of the photosphere (T ≈ 4240 K).
Only appear dark against the bright sun. Would still be brighter than the full moon when placed on the night sky!

14. Chromosphere
• The chromosphere is the next layer of the solar atmosphere found directly above the photosphere.
• This burning gas is a few thousand kilometers thick.
• Its top contains numerous spicules, which are narrow jets of rising material.
They are typically thousands of kilometers high with a 10,000 kilometer maximum height
They last 5-15 min.

15.  Obtained 24.10.2012 at 7:39 am ESTwith AIA instrument on board SDO spacecraft

16. Spicules

17. photosphere
chromosphere

20. Prominences
• Prominences are huge cloudlike structures consisting of chromospheric gases.
• Prominences are trapped by magnetic fields that extend from regions of intense solar activity.

21. prominence
 Obtained at 7:39 am ESTwith AIA instrument on board SDO spacecraft

24. Solar Flares
Solar flares are brief outbursts that normally last about an hour and appear as a sudden brightening of the region above a sunspot.
Solar flares release enormous amounts of energy, much of it in the form of ultraviolet, radio, and X-ray radiation.
Solar flares intensifies solar wind.
YouTube: Solar Flares

25. Corona • The corona is the outer, weak layer of the solar atmosphere.
The temperature at the top of the corona exceeds 1 million K (1.8 million °F) which makes it the hottest layer – other than the core.

26.  Obtained 24.10.2012 at 7:38 am EST with AIA instrument on board SDO spacecraft

27. Solar Wind
The streams of protons and electrons that boil from the corona are known as solar wind.
 Obtained at 5:38 am EST with AIA instrument on board SDO spacecraft

28. Coronal Mass Ejection

29. Aurora Borealis Solar flares can intensify the auroras.
Auroras are bright displays of ever-changing light caused by solar radiation interacting with the upper atmosphere near Earth’s poles.
Solar flares can intensify the auroras.

31. YouTube:
From Space Station
YouTube:
Over Norway

32. The Sun’s Magnetic Dynamo
Since the sun is a huge ball of gas, it rotates faster at the equator than near the poles.
This differential rotation might be responsible for magnetic activity of the sun.

33. Life Cycle of the Sun
• It is thought that a star the size of 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.”

34. Death of a Star