1. Notes-Galaxies
The Universe includes everything that we know exists, everything we can see or know about in space is included.

2. Galaxies: Most of the visible universe is made up of galaxies.
A Galaxy-is a group of stars, dust, and gases held together by gravity.
There are billions of galaxies in the universe and each one contains billions of stars.

3. Formation of Galaxies Formed from HUGE clouds of gas.
Gas particles drawn closer to each other by their gravity.
As the gas pulled together, they began to move around each other.

4. Formation of Galaxies
Leads to most galaxies, but not all, being spun to a flat, disc shape.

5. Classification of Galaxies
Classified by shape, brightness, and position in sky.

6. Classification: Elliptical
Elliptical Galaxies-
Contain mostly older stars
Stars crowded to the center
Range in shape from round to oval

7. Elliptical Galaxy

8. Classification:Spiral
Spiral Galaxies-
Disk shaped
Mix of young and old stars
Spiral arms around large dense center

9. Classification: Irregular
Irregular Galaxies-
Very irregular in shape
No dense center
Composed mostly of young stars

10. We live in the Milk Way Galaxy!
The name Milky Way came from the dim “milky” band seen across the night sky
Is an average Spiral Galaxy
Contains over 200 billion stars
100, 000 Light Years across

11. Milky Way Galaxy
It is difficult to tell exactly what our galaxy looks like because we are in it.
Scientists think it is a disk shaped spiral bound galaxy with a large spherical center.
Scientist believe we are on the outer edge of one of it’s arms

12. Hubble Images of Milky Way

13. Dark Matter There is also a lot in the sky we can’t see
We know it’s there because other things move around it
It has a gravitational pull
But scientists have no idea what it is…so they call it Dark Matter