| Question | Answer |
| Geocentric | Model that stated that the Earth was in the center of the universe
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Heliocentric | Model that stated that the sun was in the center of the universe
| Ellipse | Oval-shaped path the planets take around the sun
| Solar system | the sun, the planets, their moons, and a variety of smaller objects
| Astronomical unit | used to measure distances within the solar system
| Planet | object that orbits the sun, is round, and has cleared
| Dwarf planet | object that orbits the sun, is spherical, but has not cleared the area of its orbit
| Planetesimal | small body that combined with like bodies to form all
| Nuclear fusion | joining of hydrogen atoms to form helium occurring in the sun
| Terrestrial planet | Name given to the 4 inner planets
| Greenhouse effect | Trapping of heats and gases that causes an increase in a planet’s surface temperature
| Gas giant | Name given to the 4 outer planets
| Ring | Thin disc of small particles of ice and rock
| Asteroid belt | region of the solar system between Mars and Jupiter
| Kuiper belt | Origin of comets and asteroids
| Oort cloud | Shell of icy objects that exists in the outer reaches of the solar system
| Comet | chunk of rock or dust smaller than an asteroid
| Coma | fuzzy outer layer of a comet
| Nucleus | solid inner core of a comet
| Asteroid | Small rocky body orbiting the sun
| Meteoroid | Chunk of rock floating in space
| Meteor | streak of light produced when a meteoroid enters
| Meteorite | meteoroid found on Earth’s surface |
