1. Lesson 3.3:
The Sun

2. Lesson 3: What is the structure of the sun?
What features can you see on the sun?

3. What Is the Structure of the Sun?
No solid surface
¾ of sun’s mass is hydrogen
¼ of sun’s mass is helium
Has an interior and an atmosphere
Interior is made up of the:
Core
Radiation zone
Convection zone

4. The Sun’s Interior: The Core
Core: central region of the sun
An enormous amount of energy is produced here through nuclear fusion
Nuclear fusion: when hydrogen atoms join to form helium

5. The Sun’s Interior: The Radiation Zone
Energy produced in the sun’s core moves outward through the radiation zone
Radiation zone: a region of very tightly packed gas where energy moves mainly in the form of electromagnetic radiation
Is extremely dense; energy can take more than 100,000 years to move through this zone

6. The Sun’s Interior: The Convection Zone
Convection zone: the outermost layer of the sun’s interior
Hot gases rise from the bottom of the convection zone and cool as they approach the top
Cooler gases sink, forming loops of gas that move energy toward the sun’s surface (convection currents)

7. The Sun’s Atmosphere Stretches far into space
Layers become less dense the farther they are from the radiation zone
Mostly composed of hydrogen and helium
Includes the:
Photosphere
Chromosphere
Corona

8. The Sun’s Atmosphere: The Photosphere
Photosphere: the inner layer of the sun’s atmosphere
Considered to be the surface layer of the sun
Sun does not have a solid surface, although the gases of the photosphere are thick enough to be visible
When you look at an image of the sun, you see the photosphere

9. The Sun’s Atmosphere: The Chromosphere
Chromosphere: the middle layer of the sun’s atmosphere; means “color sphere”
The reddish glow visible around the photosphere at the start and end of a total eclipse

10. The Sun’s Atmosphere: The Corona
Corona: the outer layer that looks like a white halo around the sun; means “crown”
Extends into space for millions of kilometers
Gradually thins into streams of electrically charged particles called the solar wind

11. What Features Can You See on the Sun?
Using special telescopes to study the sun, scientists have spotted features like:
Sunspots
Prominences
Solar flares

12. Sunspots
Sunspots: dark areas on the sun’s surface; caused by areas of gas on the sun’s surface that are cooler than the gases around them
Often look small, but they can be larger than Earth
Number of sunspots varies in a regular cycle, with the most sunspots appearing about once every 11 years
Sunspots

13. Prominences
Prominences: huge loops of gas; often link different parts of sunspot regions
Prominences

14. Solar Flares
Solar flares: eruptions that occur when the loops in sunspot regions suddenly connect, releasing large amounts of magnetic energy
The energy heats gas on the sun to millions of degrees Celsius, causing the gas to erupt into solar flares

15. Solar Wind Made up of electrical particles from the sun
Solar flares can increase the solar wind, meaning that more particles reach earth’s upper atmosphere
Earth’s atmosphere usually blocks these particles, except near the North and South poles
There, they create powerful electric currents that cause gas molecules in the atmosphere to glow, creating the auroras
They can also cause magnetic storms