Basic Astronomy Dictionary
Apogee - The point in its orbit around the earth at which an object is furthest from the Earth.
Asteroid - Any of the thousands of small planets or Minor Planets.
Aurora - Glows seen over the polar regions which occur when energized particles from the Sun react with particles from the Earth .
Axis - An imaginary straight line on which an object rotates.
Black Hole - A region of space around a very small and extremely massive collapsed star within which the gravitational field is so intense that not even light can escape.
Comet - A small, frozen mass of dust and gas revolving around the sun in an ellipitical orbit.
Constellation - A grouping of stars which many times form a shape or pattern.
Eclipse - The hiding or blocking of one celestial object from another.
Galaxy - A huge collection of stars, gas and dust measuring many light years across.
Light Year - The distance which a ray of light would travel in one year. This is about 6,000,000,000,000 (6 trillion) miles.
Meteor - The luminous phenomena observed when a meteoroid is heated by its entry into the Earth's atmosphere.
Meteorite - That part of a relatively large meteoroid that survives passage through the atmosphere and falls to the surface of a planet as a mass of metal or stone.
Milky Way - The spiral galaxy containing our Sun. As seen from Earth, the constellation Sagittarius marks the direction to its center.
Nadir - That point on the celestial sphere directly opposite the zenith and directly below the observer. The lowest point.
Nebula - An interstellar cloud of gas and dust.
Nova - A star which suddenly flares up to many times its original brightness
Orbit - The closed path of one object around another.
Perigee - The point in its orbit around the Earth at which an object is closet to the Sun.
Revolve - To cause to travel in a circle or orbit.
Rotate - To turn about a center point or axis.
Satellite - A small object orbiting a larger one.
Sidereal Period - The time it takes one object to complete one orbit around another.
Solar System - The description given to the system dominated by the Sun and
including the Planets, Minor Planets, Comets, planetary satellites and
Star - A self-luminous object that shines through the release of energy produced by nuclear reactions at its core.
Supernova - A huge stellar explosion involving the destruction of a massive star and resulting in a sudden and tremendous brightening.
Zenith - The point in the sky directly above the observer. The highest point.
(From the website "Astronomy for Kids," 1999)
For more detail, go to the Advanced Astronomy Dictionary