Glossary

Aphelion - The furthest point from the Sun a planet reaches in its orbit.

Apogee - The point in its orbit around the earth at which an object is furthest from the Earth.

Asterism - A special grouping of stars that are part of a constellation. These stars form recognizable figures in the sky. An example would be the figure of Orion the Hunter. It is made up of stars in the constellation of Orion, but there are more stars in that constellation that are not part of Orion's figure.

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 elliptical orbit.

Conjunction - When one of the outer planets is on the opposite side of the Sun from the Earth. The planet is currently not visible due to the fact it is hidden by the glare of the Sun and that the planet is 'up' during the daylight hours.

Constellation - A grouping of stars which many times form a shape or pattern.

Declination - Celestial latitude measured in degrees north or south of the celestial equator.

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 just under 6,000,000,000,000 (6 trillion) miles. ((((186,000 x 60) x 60) x 24) x 365)

Meteor - The luminous phenomenon 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 before fading again.

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 Earth.

Perihelion - The nearest point a planet reaches to the Sun in its orbit.

Revolve - To cause to travel in a circle or orbit.

Right Ascension - Celestial longitude measured eastward along the celestial equator in hours of time from the vernal equinox.

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 interplanetary debris that travel in orbits around the Sun.

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.