| A | B |
|---|
| solar system | the Sun and all the bodies that orbit it |
| revolution | one full orbit of an object around another object |
| axis | center line around which the Earth rotates |
| rotation | one full spin of an object on its axis |
| space probe | spacecraft that gathers data without a crew |
| comet | frozen mass of ice and dust orbiting the Sun |
| asteroid | rocky mass that revolves around the Sun |
| satellite | an object in orbit around another object |
| Moon phase | indication of the fraction of the Moon illuminated as seen from Earth |
| light-year | distance light travels in one year |
| nebula | cloud of gas and dust in which new stars form |
| supernova | big explosion that occurs near the end of the life of some stars |
| black hole | point in space with a strong force of gravity |
| galaxy | huge system of stars, dust, and gas held together by gravity |
| constellation | group of stars that form a pattern |
