Comets - Research Article from Macmillan Science Library: Space Sciences

This encyclopedia article consists of approximately 5 pages of information about Comets.
This section contains 1,281 words
(approx. 5 pages at 300 words per page)
Buy the Comets Encyclopedia Article

The Comet's Nucleus

All of the activity in a comet originates in its nucleus, which is composed of roughly equal amounts of ices and dust. Water ice is the most abundant of the ices, comprising about 80 percent of the total. So far, only the nuclei of comets Halley and Borrelly have been imaged in detail. Comet Halley turned out to be larger, darker, and less spherical than expected by most astronomers. The images of comet Borrelly's nucleus obtained in September 2001 by NASA's Deep Space 1 spacecraft show considerable similarity with those of comet Halley. Halley's nucleus is peanut-shaped, approximately 18 kilometers (11 miles) long and 8 kilometers (5 miles) wide. The reflectivity (or albedo) is 4 percent, which is as dark as coal. The size, albedo, and approximate shape of several other cometary nuclei have been determined. Comet Halley's nucleus seems to be typical among comets with relatively short orbital periods, and there are much...

(read more)

This section contains 1,281 words
(approx. 5 pages at 300 words per page)
Buy the Comets Encyclopedia Article
Copyrights
Macmillan Science Library: Space Sciences
Comets from Macmillan Science Library: Space Sciences. Copyright © 2001-2006 by Macmillan Reference USA, an imprint of the Gale Group. All rights reserved.
Follow Us on Facebook