| A | B |
|---|
| main sequence | A star that is at the point in its life cycle in which it is actively fusing hydrogen nuclei into helium nuclei; also, the band of the Hertzsprung-Russel diagram depicting such stars |
| giant star | A large star with great luminosity and a diameter 10 to 100 times greater than that of the sun |
| supergiants | The most luminous, most massive stars, with diameters greater than 100 times the diameter of the sun |
| white dwarfs | The remnant of a giant star that has lost its outer atmosphere; the glowing stellar core |
| nebula | A large cloud of gas and dust in space |
| planetary nebula | A halo of gases that is formed by the expelled layers of a star's atmoshere |
| supernova | The brilliant burst of light that follows the collapse of the iron core of a massive star |
| neutron star | The superdence remains of a massive star that collapsed with enough force to push all of its electrons into the nuclei they orbit, resulting in a mass of neutrons |
| pulsar | A distant neutron star that emits rapid pulses of light and radiowaves instead of steady radiation |
| black hole | The final life stage of an extremley massive star, with a gravt. field so intense that light can not escape |
| galaxies | A group of millions, or even billions stars held together by gravity |
| quasar | A very distant, extr. lumi. celst. obj. that scientists consider to be a type of active galactic nuclei |
| big bang model | Thetheory holding that the universe originated from the instant expansion of an extremly small agglomeration of matter of extremly high density and temperature |
