| Term | Definition |
| star | a large celestial body that is composed of gas and that emits light |
| Doppler effect | an observed change in the frequency of a wave when the source or observer is moving |
| light-year | the distance that light travels in one year |
| parallax | an apparent shift in the position of an object when viewed from different locations |
| apparent magnitude | the brightness of a star as seen from the Earth |
| absolute magnitude | the brightness that a star would have at a distance of 32.6 light-years from Earth |
| dark-line spectra | another name for absorption spectra |
| absorption spectra | spectra composed of individual lines at specific frequencies characteristic of the gas |
| emmission spectra | a spectrum consisting of a series of bright lines against a dark background |
| continuous spectra | spectrum formed from white light contains all colors, or frequencies |
| bright-line spectra | another name for emmission spectra |
| Sol | the Latin name of our sun |
| most-common element in stars | hydrogen |
| second most-common element in stars | helium |
| apparent motion of stars | motion visible to the unaided eye, caused by the movement of Earth |
| circumpolar stars | stars that are always visible in the night sky |
| red-shift | wavelength distortion caused by a star moving away from Earth |
| -26.8 | apparent magnitude of the sun |
