| A | B |
|---|
| spectrum | the band of color produced when white light passes through a prism |
| continuous spectrum | a spectrum that shows all the colors |
| spectrograph | an instrument used to break a star's light into a spectrum |
| absorption spectrum | produced when light from a hot solid or dense gas passes through a cooler gas |
| 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 |
| light year | the distance that light travels in one year; about 9.5 trillion kilometers |
| parallax | an apparent shift in the position of an object when viewed from different locations |
| red giant | a large, reddish star late in its life cycle |
| white dwarf | a small, hot, dim star that is the leftover center of an old star |
| H-R diagram | Hertzsprung_Russell diagram, a graph that shows the relationship between a star's surface temperature and absolute magnitude |
| main sequence | the location on the H-R diagram where most stars lie |
| supernova | a gigantic explosion in which a massive star collapses and throws its outer layers into space |
| neutron star | a star that has collapsed under gravity to the point that the electrons and protons have smashed together to form neutrons |
| pulsar | a rapidly spinning neutron star that emits rapid pulses of radio and optical energy |
| black hole | an object so massive and dense that even light cannot escape its gravity |
| galaxy | a collection of stars, dust, and gas bound together by gravity |
| nebula | a large cloud of dust and gas in interstellar space |
| globular cluster | a tight group of stars that looks like a ball and contains up to 1 million stars |
| open cluster | a group of stars that are close together relative to surrounding stars |
| quasar | a very luminous, starlike object that generates energy at a high rate |
| cosmology | the study of the origin, properties, processes, and evolution of the universe |
| big bang theory | the theory that states the universe began with a tremendous explosion 13.7 billion years ago |
