| A | B |
|---|
| Milky Way | the galaxy containing the solar system; consists of millions of stars that can be seen as a diffuse band of light stretching across the night sky |
| universe | the whole cosmic system of matter and energy of which Earth, and therefore the human race, is a part |
| alien | a form of life assumed to exist outside the Earth or its atmosphere |
| outer space | any location outside the Earth's atmosphere |
| galaxy | a collection of star systems; any of the billions of systems each having many stars and nebulae and dust |
| planet | any of the nine large celestial bodies in the solar system that revolve around the sun |
| solar system | the sun with the celestial bodies that revolve around it in its gravitational field |
| Kepler | German astronomer who first stated laws of planetary motion (1571-1630) |
| aerospace | the atmosphere and outer space considered as a whole |
| interstellar space | the space between stars |
| deep space | any region in space outside the solar system |
| black hole | a region of space resulting from the collapse of a star; extremely high gravitational field |
| starship | a spacecraft designed to carry a crew into interstellar space |
| bacteria | single-celled or noncellular spherical or spiral or rod-shaped organisms |
| hydrocarbon | an organic compound containing only carbon and hydrogen |
| extraterrestrial | a form of life assumed to exist outside the Earth or its atmosphere |
| organism | a living thing that has (or can develop) the ability to act or function independently |
| micro organism | An organism that can be seen only through a microscope |
