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Table of Contents Enchanted Learning
All About Astronomy
Site Index
Our Solar System Stars Glossary Printables, Worksheets, and Activities
The Sun The Planets The Moon Asteroids Kuiper Belt Comets Meteors Astronomers

Comets
Introduction to Comets Crossing a Comet's Orbit: Meteor Showers Comet Origins Major Comets Acitvities,
Web Links

WHERE COMETS ORIGINATE

Long-period Comets (comets with an orbital period over 200 years and up to 30 million years): The Oort Cloud is a cloud of rocks and dust that may surround our solar system. This cloud may be where long-period comets originate. The Oort Cloud was named for Jan H. Oort, who proposed its existence in 1950. It has been hypothesized that the Oort Cloud is responsible for the periodic mass extinctions on Earth.

Short-period Comets (comets with an orbital period under 200 years): The Kuiper belt is a region beyond Neptune in which at least 70,000 small objects orbit. This belt is located from 30 to 50 (?) A.U.'s and was discovered in 1992. It is a region where the planet-building process was stopped in before any large objects were formed; there are only primitive remnants from the early accretion disk of the solar system, 4.5 billion years ago. The Kuiper belt may be the source of the short-period comets (like Halley's comet). The Kuiper belt was named for the Dutch-American astronomer Gerard P. Kuiper, who predicted its existence in 1951.

COMET EXPLORATION
NASA's Stardust Mission will visit the Comet Wild 2 in 2004. It will take a sample of comet particles and return them to Earth. The small spacecraft (about 770 pounds = 350 kg) was launched February 7, 1999 and will rendezvous with comet Wild 2 in January, 2004. It will return to Earth on January 15, 2006, and land in western Utah, USA.

COSMIC SNOWBALLS
There is a new and very controversial theory that comets (composed of frozen water) are constantly bombarding the Earth. These "cosmic snowballs" have (perhaps) been seen by the visible imaging system of the Polar Satellite. In theory, these frozen comets vaporize in the atmosphere, adding water vapor to the environment.

COMET WEB LINKS
Comets from NASA
Comets currently visible from the Jet Propulsion Lab.
Comet images from the Jet Propulsion Lab.
Comets from the "Nine Planets."
Comets from the University of Michigan
Current Comets by Gary W. Kronk.




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