1. Notes 10 - Galaxies Mrs. Gordon Saturday, October 03, 2015Saturday, October 03, 2015Saturday, October 03, 2015Saturday, October 03, 2015

2. 1. What is a Galaxy? A. Galaxy - a massive, gravitationally bound system consisting of stars, interstellar medium, and dark matter. A. Galaxy - a massive, gravitationally bound system consisting of stars, interstellar medium, and dark matter. B. > 100 billion galaxies in the observable Universe – each containing 100’s of billions of stars. B. > 100 billion galaxies in the observable Universe – each containing 100’s of billions of stars. Image Source and Info

3. 2. Where do we live? A. Our solar system is a tiny part of the Milky Way galaxy. A. Our solar system is a tiny part of the Milky Way galaxy. B. Our Solar System makes one full orbit every 200 million years. B. Our Solar System makes one full orbit every 200 million years. C. Most stars in the Milky Way are too close together / far away to see individually (milky look). C. Most stars in the Milky Way are too close together / far away to see individually (milky look).

4. Our Home: The Milky Way Galaxy We are always in motion….. 66,600 mi/hr 483,000 mi/hr 1.3 Million mi/hr Most of these points of light are within our own galaxy, but some points of light are actually other galaxies….

5. 3. Parts of a Galaxy FYI ~ The center of the Milky Way lies in the constellation of Sagittarius. When observations were made of the stellar velocities in the area, they were found to be particularly fast, which suggests that there is a high gravitational force acting on the stars, and therefore a high mass object in the center. This is now believed to be a black hole. constellationblack hole READ MORE HERE

6. 4. Types of Galaxies A. Spiral – flat disk, spiral arms, bulging center B. Elliptical- round to oval C. Irregular – lack a distinct shape (likely due to gravitational influence of other nearby galaxies) Add a small sketch of each

7. 5. Our Next Door Neighbor A. Andromeda Galaxy (a.k.a Messier 31 or M31) - nearest spiral galaxy to our own, approx. 2.5 million L.Y. away B. Location – visible with just your eyes in the constellation Andromeda Andromeda is the largest galaxy of the Local Group, which consists of the Andromeda Galaxy, the Milky Way Galaxy, the Triangulum Galaxy and about 30 other smaller galaxies. The 2006 observations by the Spitzer Space Telescope revealed that M31 contains one trillion (10 12 ) stars. The Milky Way and Andromeda galaxies are expected to collide / merge in ~ 3.75 billion years. The Milky Way and Andromeda galaxies are expected to collide / merge in ~ 3.75 billion years.