2. The Universe planets planets moons moons stars stars solar systems solar systems galaxies galaxies nebulae nebulae empty space empty space more? more? What’s in it?

3. What’s wrong with this model of the universe? It is not to scale.

4. Interstellar cloud of dust and gasses Interstellar cloud of dust and gasses Birthplace of stars Birthplace of stars Interstellar cloud of dust and gasses Interstellar cloud of dust and gasses Birthplace of stars Birthplace of stars Nebulae

5. Galaxies collection of stars, gas & dust held together by gravity collection of stars, gas & dust held together by gravity millions of galaxies are known to exist millions of galaxies are known to exist galaxies can contain from hundreds of thousands to one trillion stars galaxies can contain from hundreds of thousands to one trillion stars 3 major types 3 major types

6. ●Spiral galaxies ●spiral arms made of stars ●barred spiral - has two or more long arms extending away from the central “bar” cluster of stars ●Elliptical galaxies ● no spiral arms and no flattened disk (think football) ●Irregular galaxies ●have no regular shape Galaxies: The Three Types

7. Milky Way ●Spiral galaxy (Barred-Spiral) ●100,000 light-years in diameter. ●contains about 200 billion stars ●Home to Our Sun ●the Sun and Earth are located 2/3 away from center in one of the outer spiral arms ●Sun orbits central Milky Way at about 235 km/s around the center of the galaxy You are here!

8. Andromeda Galaxy nearest galaxy neighbor nearest galaxy neighbor about 2.5 million light years away about 2.5 million light years away 120,000 light years wide 120,000 light years wide A spiral galaxy A spiral galaxy The largest galaxy in our local group of galaxies The largest galaxy in our local group of galaxies

9. So Where Did It All Come From? Scientifically believed origins: 1. Big Bang 2. Oscillating Universe 3. Geocentric Model 4. Heliocentric Model

10. Big Bang The universe was created from one, instantaneous, large explosion outward The universe was created from one, instantaneous, large explosion outward most widely scientific accepted theory of the origin of the universe most widely scientific accepted theory of the origin of the universe

11. Oscillating Universe states that the universe grows outward until gravity pulls it back to the center and then expands outward over and over again states that the universe grows outward until gravity pulls it back to the center and then expands outward over and over again

12. Geocentric Model states all celestial bodies orbit the Earth states all celestial bodies orbit the Earth

13. Heliocentric Model states all objects in our solar system circle the Sun. states all objects in our solar system circle the Sun.