THE COSMOS

Known as the Geminids, the meteors radiate from the eastern sky near the night star Castor in the constellation Gemini. Meteor showers are named for the part of the sky in which the radiant lies.

Although visible for about ten days, maximum activity and prime observing this year will occur this Thursday beginning at about 10p.m. and continue until dawn.

Peak performance: During the peak performance, one can expect to see about 60 meteors per hour. Half that number will be visible this Wednesday and Friday for observers at a dark site away from the city lights and a polluted sky.

The Geminid meteor trails are usually bright, and are white or orange in color. The absence of the moon makes for excellent prospects for viewing this year's display. During the Geminids peak this Thursday, the moon will appear as a thin crescent that won't even rise until dawn. The sky will be dark enough to observe even the fainter meteors.

What's more, the Geminids are one of the few showers that are conveniently scheduled to perform well before midnight.

Good display: The Geminids are generally considered to be the best and richest of the annual showers and can always be counted upon for a good fireworks display in the sky.

Most of the meteors associated with the Geminid shower are tiny pieces of rock, metal and ice that plunge into the earth's atmosphere. Traveling at enormous speeds from the depths of space, most disintegrate instantly as they die a fiery death by friction with the air.

In the past few years the Geminids have even produced brilliant fireballs or bolides. These provide for a spectacular show of brightness and color.

Exceptional fireballs are bright enough to cast shadows and light up the landscape, these balls of fire are seen over wide areas and often have long bright trails that can last for several minutes.

Impact rare:If sounds, an explosion, or shock waves accompany a firesball sighting, this may indicate that a meteor has survived the earth's atmosphere. The result could be that a rare meteorite may have fallen.

By coordinating reports of sightings it may be possible to pinpoint the area where the meteorite may heve landed. A search for the fallen fragments can then be undertaken.

The weight and size of a meteorite can be estimated from its fluorescent trail as it streaks across the sky.

The Geminids are the remains of a comet whose orbit the earth crosses each year at this time.

It is estimated that the comet entered the inner solar system about 15,000 years ago. As it heated and broke up, it ejected a swarm of dusty particles along its orbit.

The comet responsible for the Geminids has never been identified.

Why they happen: The Geminids are putting on such an impressive annual show because their orbit is carrying the meteor swarm's most dense part into the earth's atmosphere. The orbit is slowly shifting, however, and is carrying it part away from the earth.

Since the meteor stream is drifting sideways relative to earth, our planet never passes through the same section twice.

By the year 2100, the earth and the meteor stream will have separated and the Geminids will no longer be performing their dance of death across the night sky.