| A | B |
|---|
| solar system | a system of nine planets and many other objects that orbit our sun |
| inner planets | the four solid, rocky planets closest to the sun - Mercury, Venus, Earth, and Mars. |
| outer planets | the five planets farthest from the sun - Jupiter, Saturn, Uranus, Neptune, and Pluto. |
| Mercury | in our solar system, the first planet from the sun; the second-smallest planet, it has a cratered surface like our moon. |
| Venus | in our solar system, the second planet from the sun; it is very similar in size to Earth, is blanketed with dense clouds and is very hot. |
| Earth | in our solar system, the third planet from the sun; the only planet known to support life. |
| astronomical unit | the average distance from Earth to the sun (150,000,000 km), used for measuring distances to objects in the solar system. |
| Mars | in our solar system, the fourth planet from sun. |
| data gloves | electronic gloves worn by a person controlling a robot; the gloves sense every movement the person makes and command the robot to perform identical moves. |
| Jupiter | in our solar system, the fifth planet from the sun; the largest planet, mostly gas and liquid. |
| Great Red Spot | a giant storm in Jupiter's atmosphere |
| Saturn | in our solar system, the sixth planet from the sun; it is the second-largest planet, is mostly gas and liquid, and has prominent rings. |
| Uranus | in our solar system, the seventh planet from the sun; it is large, gaseous, and is the only planet that "lays on its side" in orbit. |
| Neptune | in our solar system, usually the eighth planet from the sun; it is large and gaseous. |
| Pluto | in our solar system, usually the ninth and last planet from the sun. |
| comet | a mass of frozen gases and rock particles that orbits the sun, often developing a bright tail when it passes near the sun. |
| Oort Cloud | a cloud of comets surrounding the solar system outside Pluto's orbit; it may be the source of most comets. |
| meteor | a meteoroid that enters Earth's atmosphere and burns up as it falls |
| meteorite | a meteor that reaches Earths surface. |
| asteroid | a piece of rock, smaller than a planet, that orbits the sun; most are between the orbits of Mars and Jupiter |
| meteoroid | small pieces of rock that orbit the sun, resulting from the breakup of comets. |
