| A | B |
|---|
| star | a large, hot ball of gases, held together by gravity, that gives off its own light |
| constellation | a group of stars that appear to form a pattern |
| parallax | the apparent shift in an object's position when viewed from two locations |
| light-year | the distance that light travels in one year |
| nebula | a huge cloud of gas and dust in space |
| supernova | an exploded star |
| black hole | is an object whose gravity is so strong that even light cannot escape from it |
| absolute magnitude | a star's actual brightness |
| apparent magnitude | how bright a star looks in the Earth's night sky |
| protostar | a young star |
| galaxy | a group of star clusters held together by gravity |
| Milky Way | the Earth's galaxy |
| spectrum | a band of colors made when white light is broken up |
| big bang | the expansion of the universe rapidly |
| background radiation | comes from all directions in space and is radiation left over from the beginning moments of the universe |
