| A | B |
|---|
| constellation | group of stars that form a pattern |
| nebula | a huge cloud of dust and gas between the stars |
| galaxy | huge collection of stars |
| spiral galaxy | a galaxy that is shaped like a pinwheel; has both old and new stars |
| elliptical galaxy | a round, flat shaped galaxy with mainly old stars |
| spectroscope | an instrument that breaks up light into its characteristic colors |
| big-bang theory | a theory that says the universe began to expand with an explosion of concentrated matter and energy and continues to expand |
| gravity | force of attraction between objects |
| red giant | when a small/medium star starts to die, it will expand to form this type of star |
| supergiant star | when a large star starts to die, it will expand to form this type of star |
| white dwarf | small dense star; what a small/medium star will become towards the end of its life |
| neutron star | smallest of all the stars; remains of a large star |
| apparent magnitude | brightness of a star as it appears on the Earth |
| absolute magnitude | amount of light a star actually gives off |
| Hertzsprung-Russell diagram | a chart that show the relationship between the absolute magnitude and the surface temperature of stars |
| main sequence star | Most stars spend 90% of their "adult" life in this stage |
| parallax | an apparent change in the position of a star due to the change in the Earth's position as the Earth moves around the sun |
| nuclear fusion | combining of two atomic nuclei to produce one larger nucleus, with the release of nuclear energy |
| corona | outermost layer of the sun's atmosphere |
| chromosphere | middle layer of the sun's atmosphere |
| photosphere | innermost layer of the sun's atmosphere |
| core | center of the sun, Earth, or other object |
| prominence | violent storm on the sun that can be seen from the Earth as a huge bright arch or loop of hot gas |
| solar flare | storm on the sun that occurs when thenew moon comes directly between the sun and the Earth |
| solar wind | a continuous stream of high-energy particles released into space from the sun's corona |
| sunspot | dark area on the sun's surface |
| protostar | a new star; nuclear fusion has not started yet |
| supernova | a tremendous explosion in which a star breaks apart, releasing energy and newly formed elements |
| black hole | core of a supermassive star that remains after a supernova; has gravity so strong that even light can't escape |
