| A | B |
|---|
| interstellar matter | the gas and dust located between the stars in a galaxy |
| light-year | the distance that light travels in one year; about 9.46 trillion kilometers |
| quasar | a very luminous object that produces energy at a high rate; thought to be the most distant objects in the universe |
| red giant | a large star late in its life cycle |
| star | a large celestial body that is composed of gas and that emits light |
| supernova | a gigantic explosion in which a massive star collapses and throws its outer layers into space |
| universe | the sum of all space, matter, and energy that exist, that have existed in the past, and that will exist in the future |
| white dwarf | a small, hot, dim star that is the leftover center of an old star |
| matter | the material that everything in the universe is made of, including solids, liquids, and gases |
| big bang theory | the theory that all matter and energy in the universe was compressed into an extremely small volume that 13 billion to 15 billion years ago exploded and began expanding in all directions |
| cluster | a group of stars or galaxies bound by gravity |
| Dopler effect | an observed change in the frequency of a wave when the source or observer is moving |
| galaxy | a collection of stars, dust, and gas bound together by gravity |
| matter | the material that everything in the universe is made of, including solids, liquids, and gases |
