| A | B |
|---|
| Big Bang Theory | describes the universe as beginning with a huge explosion |
| gas giant | a large planet made up of mostly gaseous and liquid substances, with little to no solid surface |
| geocentric model | a representation of the universe in which stars and planets revolve around the Earth |
| heliocentric model | a representation of the relationship between the Sun and planets in which the planets revolve around the Sun |
| moon | a natural object that revolves around a planet |
| satellite | a natural or human-built object that revolves around another object in space |
| solar system | the Sun and the planets and other objects that orbit the Sun |
| terrestrial planets | an object in space that resembles Earth in size, in density, and in its mainly rocky composition |
| Mars | the red planet, most like Earth, 4th from the Sun |
| Inner Planets | Mercury, Venus, Earth, Mars |
| Outer Planets | Jupiter, Saturn, Uranus, Neptune, Pluto |
| Mercury | looks like Earth's moon, 1st from the Sun, almost no atmosphere, rocky surface covered with craters |
| Venus | 2nd from the Sun, dense atmosphere of carbon dioxide with sulfuric acid clouds, temperature reaches 900 degrees F |
| Jupiter | 5th from the Sun, has Great Red Spot, has thin dark rings |
| Saturn | 6th from the Sun, last planet that can be seen with unaided eye, has rings made up of ice and rock fragments |
| Uranus | 7th from the Sun, blue-green color, has thin dark rings, temperatures near -300 degrees F |
| Neptune | 8th from the Sun, discovered in 1800s, similar to Uranus |
| Pluto | 9th from the Sun, smallest planet, one known moon, Charon |
| Ptolemy | geocentric model |
| Copernicus | heliocentric model |
