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Astronomy Glossary
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
phenomenom observed when a meteoroid is heated by its entry into the Earth's
atomsphere.
Meteorite - That part of a
relatively large meteoroid that survives passage through the atomsphere 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 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 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.