1. GALAXIES Types Of Galaxies

2. How Far are Galaxies? Just as stars, galaxies are measured in light years. So what is a light year? Light travels at 186,000 miles per second A light year is measured on how far light can travel in a year. So in one year, it can travel about 10 trillion km = approximately 6 trillion miles.

3. Using a light year as a distance measurement can help determine the age of galaxies and stars. For example: The light from a star has traveled at the speed of light to reach us. It has taken the star’s light 1 million years to get here. The light we are seeing is really how the star looked a million years ago.

4. Our sun is 8 light minutes away from Earth. If the sun were to suddenly explode we would not know about it for 8 minutes!

5. In our solar system, we tend to describe distances in terms of the Astronomical Unit (AU).solar system,Astronomical Unit The AU is defined as the average distance between the Earth and the Sun. It is approximately 150 million km (93 million miles).

6. What is a galaxy? A galaxy is made of billions of stars, dust, and gas all held together by gravity. They vary greatly in size and shape. Not all galaxies look alike.

7. Spiral Spiral galaxies usually consist of two major components: A flat, large disk (bulge in center) which often contains a lot of interstellar matter and young star clusters (spiral arms). Our sun is one of several 100 billion stars in a spiral galaxy, the Milky Way. Tend to be medium to large in size.

8. Elliptical Elliptical galaxies usually have very bright centers and very little dust and gas. Is made up of mostly older stars. Are the most common, accounting for about 60% of all (known) galaxies On average, elliptical galaxies are the biggest.

9. Irregular Irregular galaxies do not have a standard shape or size. Most irregular galaxies were once spiral or elliptical galaxies but were deformed by gravitational action.

10. Contents of Galaxies Gas clouds or nebulas (gas and dust). Star clusters: Globular and Open. Globular Clusters: Groups of older stars. Within our galaxy they make the HALO.

11. Open Clusters: Closely grouped stars that are located in the spiral disk of our galaxy. Typically are the same age and have the same chemical composition.