| A | B |
|---|
| revolution | The complete orbit of one object around another object |
| third quarter | The waning-moon phase in which one-half the moon’s sunlit side is visible. |
| first quarter | The phase of the moon when it is one-quarter through its revolution |
| axis | The imaginary line running through Earth’s poles |
| phases | Different shapes of the moon as seen from Earth |
| rotation | The turning of an object on its axis |
| astronomical unit | The distance from Earth to the sun |
| meteoroid | A chunk of matter in the solar system, smaller than an asteroid |
| axial tilt | The angle that a planet’s axis is tilted from vertical |
| comet | A ball of ice, rock, and frozen gases that has an orbit that comes very close to the sun |
| season | A period of the year with a certain level of temperature and certain type of weather |
| planetary system | A system of planets revolving around a star |
| orbit | The path an object follows as it revolves around another object |
| asteroid | A chunk of rock and metal that orbits the sun between Mars and Jupiter |
| ellipse | An oval path |
