| A | B |
|---|
| Big Bang Theory | The theory of how the universe began: 13.7 billion years ago the entire universe was packed into a very tiny place. Then there was enormous explosion. After the explosion the universe expanded very quickly. |
| Dark Energy | Energy that cannot be seen. |
| Dark Matter | Stuff in the universe that doesn't give off light. |
| Universe | All stuff(matter) that exists in all space and time. |
| Galaxy | A very large group of stars held together by gravity |
| Elliptical Galaxy | Oval in shape. Have over a trillion stars. Are red/yellow in color because they have mostly old stars. |
| Globular cluster | 10,000 to 100,000 stars held together by gravity. Spherical in shape. Have mostly old red colored stars. |
| Irregular galaxy | A deformed type of galaxy that has been deformed by colliding (hitting) another galaxy. |
| Milky Way Galaxy | The galaxy in which our solar system is held in. It has a spiral shape and is about 100,000 light years across and 3,000 lightyears thick. Has a giant black hole at the center. |
| Open Cluster | A few thousand stars held together by gravity. Usually are blue in color and have glowing dust and gas. |
| Spiral Arm | An arm of a spiral galaxy where many stars are located. (Including our solar system) |
| Spiral Galaxy | Rotating disks of stars and dust. They have several arms spiraling out of a dense center. They usually have lots of gas and many young stars. |
| Star Cluster | A group of stars smaller than a galaxy. |
| Binary Star System | Two stars that orbit each other. |
| Black Hole | Something so dense that not even light can escape its gravity. |
| Main Sequence Star | A star that is going through nuclear fusion (joining two hydrogen atoms to form a helium atom) |
| Neutron Star | A star that is made up almost entirely of neutrons |
| Supernova | When a very large Red supergiant begins to run out of things to fuse it will go through a giant explosion. Often the heavier elements like gold and silver are formed from these exposions. |
| Red giant | A star that is beginning ot fuse helium atoms into the heavier elements like carbon. |
| Star | Giant ball of glowing gas that is very very hot |
