1. Samantha Lythgoe Introductory Astronomy 1040
The sun
Samantha Lythgoe
Introductory Astronomy 1040

2. What is the sun?
The sun is the nearest most easily studied star in our sky. (Bennett 285)

3. Why is the sun important?
It is the source of virtually all light, heat and energy reaching Earth, and the life on Earth’s surface could not survive without it. (Bennett 285)

4. How does the sun Shine?
Gravitational Equilibrium keeps the core hot and dense enough to release energy through the nuclear fusion of Hydrogen to Helium.
What is Gravitational Equilibrium?
It is a state of balance in which the force of gravity pulling inward is precisely counteracted by pressure pushing outward.
What is Nuclear Fusion?
The process in which two or more smaller nuclei slam together and make one larger nucleus. (bennett 302, G-6, G-9)

5. Nuclear fusion in the sun
“The core’s extreme temperature and density are just right for fusion of Hydrogen into Helium, which occurs via the proton- proton chain. Because the fusion rate is so sensitive to temperature, gravitational equilibrium acts as a thermostat that keeps the rate of fusion steady” (Bennett 302)

6. The structure of the Sun from the outside in
Corona- The outer most layer of the suns atmosphere. The corona extends several million kilometers above the visible surface of the sun and reaches about 1 million kelvin in temperature. (Bennett 302)

7. Layers of the sun
Chromosphere- A blanket of glowing gasses surrounding the sun measuring about kilometers thick and 10,000 Kelvin. (bennett 302,Layers of the sun)
Photosphere- Lowest layer of the atmosphere also the visible surface of the sun. approx. 6,000 Kelvin. This layer releases light that can be seen from earth and is Where sunspots and regions of intense magnetic fields can be found.

8. Layers of the sun
Convection Zone- 200,000 Kilometers of rising hot gasses and falling cool gasses, this process is called convection and is most easily related to boiling. Convection carries photons outward toward the surface of the sun. Convection on the sun creates energy in the form of light and heat.
Radiation Zone- In this zone energy is carried out from the core of the sun by light photons.
Core- The innermost layer of the sun. The core’s temperature reaches approx. 15 million kelvin. In the core fusion reactions occur and produce energy in the form of gamma rays and neutrinos.

9. Other Fun facts
In addition to creating a gravitational equilibrium the suns gravity holds the other planets in our solar system in orbit.
The sun is average in size, age and temperature
The sun is about 4.6 billion years old and will continue to shine for another 7 billion years.
The sun and our solar system orbit around the Milky Way galaxy once every 250 million years.
The reaction taking place in Sun is nuclear fusion, same as a Hydrogen bomb.
Each second 700 million tons of Hydrogen are converted to 695 million tons of Helium and 5 million tons of energy in the form of gamma rays.

10. Sun facts The light takes 8.3 minutes to travel from the Sun to Earth.
It takes up to 50 million years for the energy produced at the core of the Sun to reach its surface.
Solar flares are violent explosions taking place in the Sun's atmosphere occasionally. Solar flares can reach more than 100,000 miles away from the sun.
Sunspots appear as dark spots on the surface of the Sun. Sunspots are the intense magnetic regions of Sun with magnetic field strengths thousands of times stronger than the Earth's magnetic field.

11. Summary
The sun shines with energy generated by fusion of hydrogen into helium in the suns core.
Gravitational Equilibrium determines the suns interior structure and helps create a natural thermostat that keeps fusion in the sun steady.
The sun is important not only as a light and heat source, but also because it is the only star near enough for us to study in great detail.

12. Works cited
Bennett, Jeffrey, Megan Donahue, Nicolas Schneider and Mark Voit. The Essential Cosmic Perspective. 5th ed. California: Pearson/Addison-Wesley, Print.
“Nuclear Energy-Fission and Fusion.” Energystory.com.Energy Quest, , Web. 4 Dec
“Layers of the Sun.” Planetfacts.com. Planet Facts Web. 4 Dec