| A | B |
|---|
| Absolute magnitude | a measure of how bright a star really is, if all stars were the same distance from Earth |
| Apparent magnitude | a measure of how bright a star appears as seen from Earth |
| Big Bang theory | a scientific theory concerning the early development and shape of the universe from a dense state which began and is still expanding |
| Electromagnetic spectrum | a classification of all forms of radiation by wavelength and frequency; used to study components of the universe |
| Frequency | the number of times a wave passes a certain point in a given amount of time |
| Galaxy | a system of stars and associated matter, held together by gravitational attraction |
| Hertzsprung-Russell diagram | a diagram that shows the relationship between the brightness, surface temperature, and color of stars |
| Luminosity | total amount of light (energy) emitted by a star or other celestial body |
| Magnitude | the measure of the observed visible brightness of a star |
| Nebulae | clouds of dust and gas; site of star formation; remains of dead or dying stars |
| Spectra | different colors of light emitted based on the chemical composition of the light source |
| Spectroscope | a tool for observing spectral lines |
| Star | luminous globe of gas which produces its own heat and light by nuclear reaction |
| Universe | all of space and its contents |
| Wavelength | distance from any one point on a wave to a corresponding point on the next wave; crest to crest or trough to trough |
