| Term | Definition |
|---|---|
| Solar system | The sun and all the plants and other bodies that travel around it |
| Galaxy | A collection of stars,gust,and gas bound together by gravity |
| Planet | A relatively large spherical that orbits a star |
| Light year | the distance that light travels in one year; about 9.46 trillion meters |
| Star | A large celestial body that is composed of gas and that emits light; the sun is a typical star |
| Universe | Space and all the matter and energy in it |
| Luminosity | The actual brightness of an object such as a star |
| Apparent magnitude | the brightness of a star as seen from earth |
| Absolute magnitude | A measure of how bright a star would be if it were seen from a standard distance |
