| Term | Definition |
| Elliptical Galaxy |  No spiral structure. Round to cigar shape. Close cluster of solar system. Foreground Stars. Few h2 regions. |
| Barred Spiral Galaxy |  Prominent bar with curving arms. Dust Lanes. h2 regions. Foreground stars. Nucleus. |
| Spiral Galaxy |  Outstretched curving arms. Dust Lanes. Foreground Stars. Nucleus. h2 regions. |
| Irregular Galaxy |  Lacks obvious structure. Random. No shape. |
| Milky Way | An example of a spiral galaxy: |
| The Galaxy we live in. | What is the Milky Way? |
| Light Year | The distance traveled by light in one year. |
| Astronomical Unit | The average distance between the Sun and the Earth. |
| 9.46 x 10^12 | The speed of light. |
| 1.5 x 10^8 | One Astronomical Unit. |
| A group of solar systems and billions of stars. | What is a galaxy? |