COMETS IN SPACE

WHAT IS A COMET?

A comet is a large, dirty, frozen snowball. It travels in a long, elliptical, orbit around the sun. As it naers the sun, the dirty snowball begins to fall apart letting out dust and vapor. Much of this dust and vapor is ionized by the sun's massive energy. The dust and vapor is repulsed away from the sun, which forms the tail of the comet. The tail shoots out perpendicular fromthe path of the comet and never sticks to it.

CLASSIFYING COMETS

In order to classify comets, you have to study their orbital periods. There are 3 periods of a comet; Short, Intermediate, and Long periods.Periods of comet that range from 3 to 25 years is called short period. About 80 of these have been observed on repeated occassions. The famous example of these takes only 3.3 years to make one orbit around the sun is known as the Encke's Comet.

This next period is between 25 and 200 years. This period is known as the Intermediate period. The most notable and the best-known example is Halley's comet. It's probably the most observed all time. Recorded observations of Halley's Comet go back as far as 240 B.C. and it has a period 76 to 79 years. In this century, it was seen in 1910 and in 1986. Long period comets have very extended orbits which carries them up to 10,000 astronomical units from the sun.There has been 450 example that has been observed, most of which have been bright and spectacular. One of these was Comet Mikos, seen in 1957.

THE ORIGIN OF COMETS

Comets may have started fromin a huge cloud known as the Oort cloud that is thought to have surround the solar system. Comets are released from the cloud and pushed toward the inner regions of passing stars of the solar system by its gravitational attraction of passing stars. Astronomers can't actually see the cloud, however its existence is based only on theory. Another thought is that in its orbit, the sun encounters clouds of gas and dust when going through these clouds. Its gravitational pull attracts particles from the cloud that follows it in its orbit. These particles work together to form the nucleus of a comet.

WHAT ARE COMET MADE OF?

Hyakutake's tail, is made of dust and gas driven off the icy comet nucleus by the heat of the sun and blown away by the solar wind. Encamped solar ultraviolet light the gas molecules breakdown and produce an original glow. This bright glow is responsible for the light emitting from the tail.

I wrote this page, the one and only Kim Cadien at BCC/Summer Science on July 21, 1998.