| A | B |
|---|
| Astronomical unit | Earth’s average distance from the Sun, which is approximately 150 million kilometers |
| Eclipse | An event during which one object in space casts a shadow onto another |
| Terrestrial planet | Earth or a planet similar to Earth that has a rocky surface |
| Tectonics | The processes in which the motion of hot material under a crust changes the crust of a space body |
| Volcanism | The process of molten material moving from a space body’s hot interior onto its surface |
| Gas giant | A large planet that consists mostly of gases in a dense form |
| Ring | In astronomy, a wide, flat zone of small particles that orbit around a planet’s equator |
| Asteroid | A small, solid, rocky body that orbits the Sun |
| Comet | A body that produces a coma of gas and dust |
| Comet | A small, icy body that orbits the Sun |
| Meteor | A brief streak of light produced by a small particle entering Earth’s atmosphere |
| Meteorite | A small object from outer space that passes through Earth’s atmosphere and reaches the surface |
