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Name: Etljr
Status: Other
Age: N/A
Location: N/A
Country: N/A
Date: Prior to 1993

As far as comets are concerned, what is the area outside of our solar system called and how does it relate to the formation of comets. Also, how many known comets are on record; which is the largest, smallest, etc.

There is a region (still considered in our solar system) well beyond the orbit of Pluto called the Oort Cloud. This is where most comets spend most of their time because they have highly elliptical orbits. I am not sure how many periodic (returning) comets are on record -- certainly hundreds, maybe thousands. The most famous and one of the largest is Halley's Comet. Their is no limit on how small a comet can be, but very small comets have to get very close to the sun to be detected. As for comet formation, most astronomers believe they are remnants of the formation of the solar system. The Oort Cloud (note: singular tense) is the theoretical region associated with our solar system where most comets spend most of their time. This is possible because most comets have highly elliptical orbits. Look for a college undergraduate text book on astronomy. This may be beyond the level of a high school student, but a possible project might be to use the orbital parameters of known reappearing comets to calculate the dimensions of the Oort Cloud. It would also be interesting to learn more about Prof. Oort and how he came up with the idea.

John Hawley

The best write-up on the Oort cloud of the astronomy texts I have is in "Exploration of the Universe" by Abell, Morrison, and Wolff. Some astronomers believe that in addition to the Oort cloud, there is another reservoir of comets (the source of "short-period" comets) called the Kuiper belt. I consulted the online Reader's Guide and found some magazine articles that, from the abstracts, look promising: Sky and Telescope Jan. '93 p. 15, p. 26-9; Sky and Telescope Apr. '93 p. 44-5 <-- about Jan Oort; Astronomy Sept. '92 p. 40-7; Discover Feb. '91 p. 8

Ronald Winther

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