1. Astronomy Contents of the universe We live in the solar system. Earth orbits the sun every yr in elliptical orbit. Distance Earth to sun 1 AU

2. Birth of the Solar System Solar system born ~4.5 BYA 2 min http://www.youtube.com/watch?v= qfdDWdZcpOw

3. Our Solar System planets/moons/asteriods

4. Asteroid Belt mars-Jupiter

5. Icy Comets -All orbit the sun -very elliptical orbits

6. Solar system is part of the milky way galaxy. Orion Arm. The galaxy revolves around black hole. Sun revolution ~ 250 million y.

7. Galaxies –large aggregates of stars, gas, & dust containing ~ 100 billion (10 11 ) stars ranging in diameter from 1,500 to 300,000 light-years across. Orbit central point. Av distance btw stars 10 ly.

8. Stars can form stellar clusters w/i galaxies – smaller groups of stars held by gravity. ~ 1000’s of stars.

9. Constellations – star groups not necessarily near each other.

10. Galaxies form groups too. Galactic Clusters Nearest cluster = Virgo cluster

11. It’s a long way btw stars. Use Light Years LY Calculate the d light travels in 1 yr. 1 LY = 9.46 x 10 15 m.

12. Relative Distances Universe~1.5 x 10 26 m 15 Billion LY Between galactic clusters~10 8 LY Betw galaxies~10 6 LY Local group (20 gal)2 x 10 6 LY radius Milky Way10 5 LY dia, 10 4 LY thick 10 LY btw stars

13. Powers of 10 Film http://www.youtube.com/watch?v=tnhken4_-A0

14. Earth’s Rotation makes stars appear to rotate on fixed sphere. Rotation is around Polaris on 24 h cycle. Sun/planets wander through stellar backdrop.

15. From Earth Stars Appear to be embedded in sphere.

16. Stars rotate around Polaris 24 hr cycle rise east set west Stars appear fixed on sphere relative to each other. http://www.youtube.com/watch?v=JCr_Pz4h2Bw

17. Planetary Motion Wanderer & Retrograde

18. Hwk Sheet: Intro to Astrophysics