1. { On the Shoulders of Giants Organization of the universe

2. THE UNIVERSE: 3 theories 1. Open, expands forever 2. Closed, like a saddle 3. expanding and contracting

3. Galaxies: contain stars, huge clouds of gas and dust (nebulae) which revolve around a nucleus. Three types

4. Spiral galaxies: Very organized like our Milky Way galaxy

5. Elliptical Galaxies: Sphere or flattened disk, older stars, little gas and dust

6. Irregular galaxies: No specific shape

7. Stars: Made up of mostly Hydrogen and Helium. Formed by collapsing gas and dust

8. Nebulae: Birthplace of stars, globs of gas and dust. Full of radio, UV, IR, and X- Rays

10. Star Clusters: Open (Pleiades) and Globular(Hercules)

11. Single star: Our sun. Single star systems are relatively uncommon.

12. Binary Star systems: Double Stars. Very common type of star system.

13. Novas: nuclear explosion of a white dwarf star. Causes increased brightness of a star.