| A | B |
|---|
| universe | the sum of all matter and energy that exists |
| star | huge ball of hot gas that emits light |
| galaxy | a collection of millions or billions of stars bound together by gravity |
| light year | the distance that light travels in one year |
| interstellar matter | gas and dust found between the stars in a galaxy |
| cluster | a group of galxies bound by gravity |
| red shift | a shift toward the longer wavelength end of the spectrum |
| big bang theory | states that the universe began about 13 billion years ago in an enormous explosion |
| constellation | a group of stars that appear to make a pattern as seen from Earth |
| red giant | large star in which helium fusion is occuring |
| white dwarf | small dense star that remains after fusion stops in a red giant |
| supergiant | an extremely large star that creates elements as heavy as iron |
| supernova | a powerful explosion that occurs when a massive star dies |
| neutron star | a dead star with the density of atomic nuclei |
| black hole | an object so massive that even light isn't fast enough to escape its gravity |
| planet | a relatively large object that orbits a star |
| solar system | the sun and all the objects that orbit around it |
| asteroid | small rocky object that orbits the sun |
| nebular model | the most widely accepted model of the formation of the solar system |
| phases | the different apparent shapes of the moon or a planet due to their relative position compared to the Earth and the sun |
| eclipse | an event that occurs when one object passes into the shadow of another object |
