| A | B |
|---|
| star | an object that produces its own energy, including heat and light |
| big bang | The __________________ theory states that the universe started with a single point and has been expanding ever since |
| protostar | When a nebula contracts and hydrogen atoms begin to combine and form atoms of helium, it becomes a _________________, or beginning star |
| red giant | A _________________ is a stage in the cycle of a star. It is many times larger than the original star. |
| white dwarf | The ___________________ stage is the end of a medium-sized star's life. |
| supernova | A star that begins life with much more hydrogen than a medium-size star (our Sun) ends its life as an exploding star called a ___________________ |
| black hole | A _________________ is an object that is so dense and has such powerful gravity that nothing can escape from it, not even light. |
| temperature | Stars are classified by their size, color, and _______________ |
| Sun | The ___________ is a medium-sized yellow star whose surface temperature is about 10,832 degrees Fahrenheit |
| constellations | Patterns of stars in the sky are ___________________ |
| light-year | A huge measuring unit that astronomers use to describe distance is called a _____________. It is the distance that light travels in a year. |
| galaxy | A _________________ is a huge, very distant collection of stars. |
| Milky Way | Our solar system is in an arm of a spiral galaxy called the ___________________ |
| binary stars | Two stars that form near each other and rotate around each other are called ________________ |
| irregular | There are three types of galaxies. They are spiral, elliptical, and _______________ galaxies |
| nebula | All stars form out of a _____________ which is a huge cloud of gases and dust |
