Term | Definition |
Terrestrial Planets | One of the highly dense planets nearest to the sun; Mercury; Venus; Earth; Mars |
Gas Giants | a planet that has a deep, massive atmosphere, such as Jupiter, Saturn, Uranus, or Neptune |
Astronomical Unit | the average distance between Earth and the sun; approximately 150 million kilometers |
Revolution | the motion of a body that travels around another body in space; on complete trip along an orbit |
Rotation | the spin of a body on its axis |
Dwarf Planet | a celestial body that orbits the sun, is round because of its own gravity, but has not cleared its orbital path |
Asteroid Belt | the region of space between the orbit paths of Mars and Jupiter in which most asteroids are located |
Kuiper Belt | a disk-shaped region on the edge of the solar system that contains masses of ice and icy rock, supposed to be the source of comets |
Oort Cloud | a region of the solar system beyond the Kyper Belt in which billions of comets move in nearly circular orbits unless one is pulled into an elliptical orbit by a passing star. |
Comet | a small body that gives off gas and dust as it passes close to the sun; a typical comet moves in an elliptical orbit around the sun and is made of dust and frozen gases |
Asteroid | a small, rocky object that orbits the sun; most asteroids are located in a band between the orbits of mars and jupiter |
Meteoroid | a relatively small, rocky body that travels through space |
Meteor | a bright streak of light that results when a meteoroid burns up in earth's atmosphere |
Meteorite | a meteoroid that reached earth's surface without completely burning up |
Prograde Rotation | When a planet rotates on it's axis at a less than 90 degree angle clockwise |
Retrograde Rotation | When a planet rotates on its axis at a 90 or higher degree tilt or in a counter clockwise rotation |
Solar System | the sun and all of the planets and other bodies that travel around it |