1. Sun
Lesson 3

2. Sun The sun is a star located at the center of our solar system.
The nearest star from earth and our engine for life.
It is a medium-sized yellow star.
It contains approximately 98 % of all matter in the solar system

3. Characteristics of the Sun

4. Sun’s Structure

5. 3 Layers of the Sun
CORE
The core starts from the center and extends outward to encompass 25 percent of the sun's radius. Its temperature is greater than 15 million degrees Kelvin. At the core, gravity pulls all of the mass inward and creates an intense pressure. The pressure is high enough to force atoms of hydrogen to come together in nuclear fusion reactions.

6. 2. RADIATION ZONE It extends outward from the core, accounting for 45 percent of the sun's radius. In this zone, the energy from the core is carried outward by photons, or light units. 3. CONVECTION ZONE It is the final 30 percent of the sun's radius. In the convective zone, the energy is transferred much faster than it is in the radiative zone this is because it is transferred through the process of convection. Hotter gas coming from the radiative zone expands and rises through the convective zone. It can do this because the convective zone is cooler than the radiative zone and therefore less dense.

7. SUN’S 3 ATMOSPHERIC LAYER
1. PHOTOSPHERE It is the innermost region of the sun's atmosphere and is the region that we can see. "The surface of the sun" typically refers to the photosphere. It appears granulated or bubbly, much like the surface of a simmering pot of water.

8. 2. CHROMOSPHERE It extends above the photosphere to about 2,000 kilometers. The chromosphere is thought to be heated by convection within the underlying photosphere. 3. CORONA It is the final layer of the sun and extends several million miles or kilometers outward from the other spheres. It can be seen best during a solar eclipse and in X-ray images of the sun. Although no one is sure why the corona is so hot, it is thought to be caused by the sun's magnetism.

9. Phenomena at the Sun’s Surface
The Sun’s magnetic field controls the motion of gases in the corona, creating delicate streamers which are seen from the Earth as flares and arching prominences.

10. Solar flares – Huge Outburst! The explosive event on the solar surface.
Prominences – masses of glowing gas above the Sun’s bright surface.
Sunspots – darker patches! They are cooler that the surrounding regions of the photosphere.
Solar wind – often give off ultraviolet light and x-rays that heat up the earth’s upper atmosphere.

11. Generation of Energy by the Sun
The sun generates its energy through a nuclear fusion
Fusion occurs at the center of the sun
Hydrogen atoms collide into each other and fuse into atoms of helium. Energy is release through this process!
Fusion of deuterium with tritium creating helium-4, freeing a neutron, and releasing