| A | B |
|---|
| planet | planasthai, which means "to wander" |
| Ptolemy | Earth centered universe |
| Copernicus | Sun-centered "solar system" |
| Galileo Galilei | discovered phases of Venus, moons of Jupiter |
| inner planets | Mercury, Venus, Earth, Mars |
| outer planets | Jupiter, Saturn, Uranus, Neptune, Pluto |
| Kepler | discovered...planets travel at different speeds |
| Mercury | closest planet to sun, very small |
| Venus | greenhouse effect, dense atmosphere |
| Earth | only planet KNOWN to have life |
| Astronomical Unit | distance from the sun to earth |
| Viking 1 and 2 | first probes to land on Mars |
| Mars | the "Red Planet" |
| Pathfinder, Global Surveyor | newest Mars probes |
| Phobos and Deimos | Martian moons |
| Jupiter | largest planet |
| Great Red Spot | giant storm on Jupiter |
| Galileo (probe) | probe sent to Jupiter |
| Io | moon of Jupiter, volcanic activity |
| Saturn | second largest planet, many rings |
| Voyager 1 and 2 | probe to Jupiter and outer planets |
| Uranus | planet , rotates like a rolling ball |
| Neptune | Great Dark Spot |
| Pluto | smallest planet, farthest from sun |
| Cassini | probe will reach Saturn in 2004 |
| Shoemaker-Levy 9 | comet that crashed into Jupiter, 1994 |
| Magellan (probe) | mapped Venus |
| greenhouse effect | makes Venus the hottest planet , 470 degrees Celsius |
| Mariner 10 | only space probe sent to Mercury |
| Halley's Comet | orbits the sun every 76 years |
| Oort Cloud | source of many comets, beyond Pluto |
| comet | dirty snowball, frozen ice and rock |
| meteor | meteoroid that burns up in atmosphere |
| asteroid | rock similar to planets |
| meteorite | meteoroid that hits the earth's surface |
| Ceres | largest asteroid |
