| Word |
 |
|
| Definition |
|
|
| astronomical unit (AU) |
the average distance between the Earth and the sun, or approximately 150,000,000 km |
| terrestrial planets |
the small, dense, rocky planets of the inner solar system |
| prograde rotation |
the counter-clockwise spin of a planet or moon as seen from above the planet's north pole |
| retrograde rotation |
the clockwise spin of a planet or moon as seen from above the planet's north pole |
| gas gaints |
the large, gaseous planets of the outer solar system |
| satellite |
a natural or artifical body that revolves around a planet |
| phases |
the different appearance of the moon due to varying amounts of sunlight on the side of the moon that faces the Earth |
| eclipse |
an event in which the shadow of one celestial body falls on another |
| comet |
a small body of ice, rock, and cosmic dust loosely packed together that gives off gas and dust in the form of a tail as it passes close to the sun |
| asteroid |
a small, rocky body that revolves around the sun |
| asteroid belt |
the region of the solar system most asteroids occupy |
| meteoroid |
a very small, rocky body that revolves around the sun |
| meterorite |
a meteoroid that reaches the Earth's surface without burning up completely |
| meteor |
a streak of light caused when a meteoroid or comet dust burns up int he Earth's atmosphere before it reaches the ground |
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