| A | B |
|---|
| nebular theory | states that the solar system began as a huge cloud of dust and gas |
| orbit | path taken when moving around an object |
| period of revolution | time it takes to make one revolution around the sun |
| retrograde rotation | reverse motion when a planet rotates from east to west |
| greenhouse effect | process in which carbon dioxide forms a "heat blanket" |
| asteroid belt | region between Mars and Jupiter where rocky bodies are found |
| comet | object made of ice, gas, and dust that travels through space |
| meteoroid | chunk of metal or stone that orbits the sun |
| meteor | a "shooting star" |
| meteorite | a meteor that strikes the surface of the Earth |
