| A | B |
|---|
| Geocentric Model | Earth is considered the center of the solar system and everything else revolves around it |
| Heliocentric Model | Sun is considered the center of the solar system and everything else revolves around it |
| Ptolemy | Came up with the geocentric model |
| Copernicus | Came up with the heliocentric model |
| Galileo | Found evidence that supported the ideas of Copernicus |
| Kepler | Discovered that planets travel around the Sun in ellipses, not circles |
| Astronomical Unit (AU) | The average distance from Earth to the Sun (150,000,000 km) |
| Planet Classification by Size | Terrestrial and Jovian (Gas Giants) Planets |
| Planet Classification by Location | Inner Planets (orbit between Sun and asteroid belt) and Outer Planets (orbit outside of asteroid belt) |
| Planet Classification by Location | Inferior Planets (orbit between Earth and the Sun) and Superiod Planets (orbit beyond Earth) |
| Nebula | A huge cloud of gas, ice and dust which formed into our present solar system |
| Extrasolar Planets | Planets in orbits around stars other than the Sun |
| Mercury | Closest planet to the Sun, covered by craters, no atmosphere |
| Venus | Second planet from the Sun, dense atmosphere which causes greenhouse effect |
| Earth | Third planet from the Sun, allows life to exist |
| Mars | Fourth planet from the Sun, red planet, has seasons, thin atmosphere, water may have once been present |
| Jupiter | Fifth planet from the Sun, largest planet, gaseous, has Great Red Spot |
| Saturn | Sixth planet from the Sun, ringed planet |
| Uranus | Seventh planet from the Sun, axis of rotation is tilted on side |
| Neptune | Eighth planet from the Sun, has rings |
| Comet | Composed of dust and rock particles mixed with frozen water, methane, and ammonia |
| Asteroid | Rocky objects formed from material similar to that of the planets; found in a belt between the orbits of Mars and Jupiter |
| Meteoroids | Rocky objects orbiting within the solar system that formed when asteroids collided or when comets passed too close to the Sun, leaving a trail of debris |
| Meteorites | Meteoroids that do not burn up completely in the atmosphere and strike Earth |
| Sedna | An object in the solar system that has been labeled a distant planetoid |
| Characteristics of Living Things | Take in nutrients, use nutrients for energy, produce waste, reproduce |
| Extraterrestrial Life | Life on other worlds |
| Europa | One of Jupiter's Moons; may have a liquid ocean that could harbor life |
