2. The sun

3. Aim: What are some characteristics of the sun? I. Sun – the closest star to earth. a.Star – creates its own energy by fusing hydrogen into helium (nuclear fusion). b.The sun is an average star and can be found in the middle of the Hertzsprung- Russell diagram. (p. 15 of ESRT)

4. 1.Hertzsprung-russell 1.Hertzsprung-russell diagram diagram – Groups stars by color (an indication of temperature) and by how much light they give off. What is the color of the coolest stars? Hottest stars?

5. C. Some interesting sun facts 1.Mass = 300,000 times the earth 2.Surface temperature = 9900 o F 3.Core temperature = 27,000,000 o F 4.Composition = 71% H, 27% He, and 2% heavier elements.

9. Solar Prominence

10. Aurora

11. II. Other Astronomical Terms A.Galaxy - a huge body of stars and other matter in space. Ex: our Sun is one of roughly 100 billion stars in the Milky Way. B.Milky Way – a spiral galaxy. Our solar system is located in the spiral arm of the Milky Way, far from the center of it. Approximately 150, 000 light years across!

12. How do we know that the universe is expanding? Red Shift (Doppler Shift) – light is traveling away from us. Long waves. Blue Shift – light is traveling towards us. Short waves.

13. Electromagnetic Spectrum

14. The Milky Way

15. 100,000 Light Years across