1. Objectives
Learning Target: Develop a model based on evidence to illustrate the life span of the sun and the role of nuclear fusion in the sun’s core to release energy in the form of radiation.
Success Criteria:
Create a model to show the structure of the sun.
Describe how helium and energy is created through fusion processes in the sun using hydrogen as its fuel source.
Explain that the sun (like all stars) has a lifespan based on initial mass and that our sun’s life span is about 10 billion years.
Using a model, predict how the relative proportions of hydrogen to helium change as the sun ages.

2. Structure of the Sun
Objective: Create a model to show the structure of the sun.
Notes should include pictures and important terms.
We will discuss:
Layers of the Sun
Interior
Exterior/Atmosphere
Important features

3. Layers of the Sun Sun’s interior Sun’s atmosphere
Core – where hydrogen fusion happens.
Radiative zone – energy carried toward surface by radiation (as light).
Convective zone – energy carried toward surface by convection (as heat).
Sun’s atmosphere
Photosphere – lowest layer – emits visible light – what we see.
Chromosphere – middle layer – transparent.
Corona – upper layer – transparent.

5. INTERIOR of the Sun – 3 layers

6. ATMOSPHERE of the Sun – 3 layers

7. The bright visible surface of the Sun is called the photosphere.
When looking at the Sun, the edges appear orange and darker than the central yellow region. This is known as limb darkening.

9. Upon closer inspection, the Sun has a marbled pattern called granulation, caused by the convection of gases just beneath the photosphere.

10. During an eclipse, sometimes you can see the layers of the Sun’s atmosphere just above the photosphere, which emits only certain wavelengths of light, resulting in a reddish appearance. We call this the sphere of color, or chromosphere.

11. The solar chromosphere is characterized by jets of gas extending upward called spicules.

12. THE SOLAR CORONA – source of the Solar Wind
This x-ray image shows the million-degree gases.
Seen in visible light during an eclipse.

13. The Sun undergoes differential rotation.
The rotation period of the Sun’s gases varies from 25 days in the equatorial region to 35 days near the solar poles.

14. Therefore, the magnetic field lines of the Sun become intertwined after several rotations, creating regions of intense magnetic fields and thus producing sunspots and other spectacular features.

15. The Sun’s Magnetic Field Creates Different Features
Sunspots – areas of concentrated magnetic field lines.
Prominences – magnetic loops above sunspots, can carry plasma (hot ionized gas).
Flares – twisted magnetic field lines relax and release huge amounts of X-rays.
Coronal Mass Ejections (CMEs) – twisted magnetic field lines relax and release huge amounts of plasma (up to 4 million mph).

16. Sunspots Overlapping sunspots
Sunspots have two regions: the inner, darker umbra and the outer penumbra.

17. Sunspots are regions of intense magnetic fields

18. The number of sunspots on the photosphere varies over an eleven-year cycle.
Sunspot Maximum
Sunspot Minimum

19. Sunspots can be used to determine the rate of the sun’s rotation.

20. Vital information about Sunspots
Areas of reduced temperature
Visible from Earth
Large Amount of Magnetic Activity
Can affect electronics due to the amount of geomagnetism produced.

21. Ionized gases trapped by magnetic fields form prominences that arc far above the solar surface.
Sometimes these gases are ejected into space.

22. Solar prominences Looping shape
Relatively cool clouds of gas suspended above the sun
Controlled by magnetic forces

23. Violent eruptions called solar flares release huge amounts of X-rays
Violent eruptions called solar flares release huge amounts of X-rays. Solar flares are often associated with coronal mass ejections.

24. On the sun, coronal mass ejections occur when solar magnetic field lines snake around each other, forming the letter "S". Usually, they go past each other. But if they connect, it's like a short circuit. The mid-section breaks loose and drives out a coronal mass ejection.

25. Coronal Mass Ejections (CMEs) typically expel 2 trillion tons of plasma at up to 4 million mph.
It reaches Earth two to four days later, and is fortunately deflected by our magnetic field.
An x-ray view of a coronal mass ejection

26. By following the trails of gases released during a coronal mass ejection, we can map the Sun’s magnetic field.

27. Solar flares Exploding areas on the sun
Releases huge amounts of energy
Magnetic field and atmosphere protect Earth from harmful effects
Airline pilots and Astronauts are most impacted by effects
Cause Aurora Borealis (Northern Lights)

28. Nuclear Fusion
Objective: Describe how helium and energy is created through fusion processes in the sun using hydrogen as its fuel source.

29. Let’s Review Fusion!! Hydrogen is the fuel!!!
Nuclei fuse to form Helium and energy as a product
Extreme temperatures are required for fusion to occur due to the repulsive forces of the nuclei (nuclei are positively charged)
The sun is stable because the force of gravity is balanced by the thermal pressure created by the reactions in the core

30. The Sun is powered by thermonuclear fusion, which converts hydrogen into helium. Matter gets turned into energy in the process.
E = mc2

31. RADIATION PRESSURE FROM
The Sun’s interior is held stable by a balance between radiation pressure forces and gravity, in a condition called hydrostatic equilibrium.
GRAVITY – pulls in
RADIATION PRESSURE FROM
HYDROGEN FUSION –
pushes out

32. THE SOLAR INTERIOR

33. Lifespan of the Sun
Objective: Explain that the sun (like all stars) has a lifespan based on initial mass and that our sun’s life span is about 10 billion years.
Our sun is a less massive star and will end as a white dwarf.
We are currently 5 billion years into its lifespan
Let’s watch a video to help us put all of this information together!

35. Aging Sun and Nuclear Energy
Objective: Using a model, predict how the relative proportions of hydrogen to helium change as the sun ages.

36. Two (2) Hydrogen atoms fuse to make One (1) Helium atom theoretically but…
Energy is released as atoms fuse and thus mass is lost as energy
It actually takes 4 Hydrogen atoms to make 1 Helium atom

37. Time to Think! Let’s try to make sense of all of this!
Read and complete the worksheet:
How Does the Sun Get It’s Energy
Then, read the article cited below
Red Giant Stars: Facts, Definition & the Future of the Sun. Retrieved September 11, 2016, from
Create a timeline to show the lifecycle of our sun showing how hydrogen, helium, mass, fusion and gravity play a role in the life and death of our sun.