| A | B |
|---|
| star | a large celestial body that is composed of gas and that emits light; the sun is a typical star |
| luminosity | the actual brightness of an object such as a star |
| apparent magnitude | the brightness of a star as seen from Earth |
| absolute magnitude | a measure of how bright a star would be if it were seen from a standard distance |
| nebula | a large cloud of gas and dust in interstellar space, a region in space where stars are born |
| neutron star | a star that has collapsed under gravity to the point that the electrons and protons have smashed together to form neutrons |
| white dwarf | a small, hot, dim star that is the leftover center of an old sunlike star |
| H-R diagram | Hertzsprung Russell diagram, a graph that shows the relationship between a star's surface temperature and absolute magnitude |
| supernova | a gigantic explosion in which a massive star collapses and throws its outer layers into space |
| main sequence | the location on the H-R diagram where most stars lie: it has a diagonal pattern from the lower right (low temperature and luminosity) to the upper left (high temperature and luminosity) |
