| A | B |
|---|
| spectroscope | instrument that breaks up the light from a star into its characteristic colors |
| prism | piece of glass that bends light so it forms a spectrum |
| galaxy | huge collection of stars |
| red shift | shift toward the red end of the spectrum of a star moving AWAY from the earth |
| blue shift | shift toward the blue end of the spectrum of a star moving TOWARD the earth |
| constellation | a group of stars that form a pattern |
| big bang theory | theory that states the universe was formed by the explosion of very dense and hot matter compacted into a small area |
| gravity | force of attraction between objects |
| Milky Way | galaxy in which the earth's solar system is located |
| elliptical galaxy | type of galaxy that can vary in shape from nearly spherical to a flat disk |
| irregular galaxy | type of galaxy with no definite shape |
| spiral galaxy | type of galaxy that is made of a thick mass of material and flattened arms that spiral around the center |
| nebula | gas and dust cloud |
| nebular theory | theory that states that the solar system began as a huge cloud of gas and dust |
| open clusters | large, loosely organized groups of stars |
| binary stars | pair of stars that revolve around each other |
| nova | star that suddenly increases in brightness and soon after slowly becomes dimmer |
| Polaris | another name for the North Star |
| eclipsing binaries | binary star system in which one star blocks out the light from the companion star |
| giant | a star with a diameter 10 to 100 times that of the sun |
| supergiant | star with a diameter up to 1000 times that of the sun |
| white dwarf | small, very dense star |
| neutron star | smallest type of star that results from the supernova of a massive star |
| magnitude | measure of a star's brightness |
| apparent magnitude | measure of a star's brightness as it appears from earth |
| absolute magnitude | actual amount of light a star gives off |
| variable star | star with a brightness that varies |
| cepheid variable (pulsating variable) star | star that varies in brightness |
| parallax | apparent change in the position of a star in the sky due to the change in the earth's position as it moves around the sun |
| supernova | tremendous explosion in which a star breaks apart, releasing energy |
| black hole | core of a supermassive star after a supernova |
