| A | B |
|---|
| Came up with the sun-centered universe theory | Copernicus |
| Moons going around Jupiter | Galileo observed this to help prove Copernicus's theory |
| Why Pluto isn't a planet anymore | Its orbit crosses over Neptune's |
| Rotation (spin) on axis | Gives planets their day |
| Revolution (orbit) around the sun | Gives planets their year |
| The farther the planet from the sun | the bigger the planet's orbit |
| Outer planets | Bigger, gaseous, Mostly hydrogen and helium, have rings, have many moons |
| Inner planets | Smaller, rocky, few or no moons, no rings |
| Meteors | pieces of asteroids or comets that can enter earth's atmosphere |
| Comets | originate outside of the solar system, rarely enter earth's atmosphere |
| Asteroid Belt | area where debris that were too small to form planets orbits the sun |
| Between which two planets is the asteroid belt? | between Mars and Jupiter |
| Why scientists study meteorites | They're untouched since the formation of the universe |
| Meteorites | meteors that have crashed down to Earth's surface |
| Meteoroids | Meteors that are still in space above Earth's atmosphere |
| Kuiper Belt | Disc-shaped region just beyond Neptune where most dwarf planets are |
| Oort Cloud | Shell of icy objects at the edge of the solar system |
| Formation of the Solar System | Leftovers from the Nebula that formed the Sun |
