| A | B |
|---|
| year | The length of time it takes a planet to orbit around the sun. |
| terrestrial | "earth-like" or rocky |
| rotation | To turn in a circular motion on an axis. |
| gaseous | composed of substances that are neither solid or liquid. |
| day | The length of time it takes a planet to rotate on its axis. |
| axis | An imaginary line passing through the center of the earth from the north pole to the south pole |
| AU | the distance from the sun to earth. |
| gravity | The force that attracts one object to another. |
| universe | All created things. |
| orbit | The path of a heavenly body as it rotates around another body. |
| constellation | A fixed group of stars. |
| continent | Large mass of land. |
| galaxy | A group or system of stars and other heavenly bodies. |
| planet | A heavenly body that revolves around the sun. |
| solar system | The group of planets, their satellites (moons), comets, meteors, asteroids, and so forth that revolve around the sun. |
| star | Any celestial body that gives off light. |
