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A celestial body, observed only in that part of its orbit that is relatively close to the sun, having a head consisting of a solid nucleus surrounded by a nebulous coma up to 2.4 million kilometers (1.5 million miles) in diameter and an elongated curved vapor tail arising from the coma when sufficiently close to the sun. Comets are thought to consist chiefly of ammonia, methane, carbon dioxide, and water.

[Middle English comete, from Old English comēta, from Late Latin, from Latin comētēs, from Greek komētēs, long-haired (star), comet, from komē, hair.]

com′et·ar′y (-ĭ-tĕr′ē), co·met′ic (kə-mĕt′ĭk) adj.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
ThesaurusAntonymsRelated WordsSynonymsLegend:
Adj.1.cometary - of or relating to or resembling a comet
Based on WordNet 3.0, Farlex clipart collection. © 2003-2012 Princeton University, Farlex Inc.
References in classic literature ?
"The public temper will soon get to a cometary heat, now the question of Reform has set in.
The outline which would bound my walks would be, not a circle, but a parabola, or rather like one of those cometary orbits which have been thought to be non-returning curves, in this case opening westward, in which my house occupies the place of the sun.
Other astronomers quickly confirmed its new cometary appearance.
His early work with this instrument was deep sky imaging, but cometary imaging soon became his main interest, and he contributed many fine images and measurements to the Comet Section of the BAA and The Astronomer magazine.
Second, perhaps earlier cometary water was made up of the lighter hydrogen form.
Ogliore and team found no evidence for extinct 26Al, meaning the cometary fragment formed after nearly all the 26Al had decayed.
In an e-mail last year, British amateur Sakib Rasool suggested writing about young stellar objects with cometary reflection nebulae.
The distribution of hydrogen and water beneath Earth's surface suggests to many geochemists that water hasn't mixed deep into the planet, so they thought that the cometary bombardment applied a veneer of water to the dry planet relatively late in its formative period.
A second, more massive ring of colder dust located at the far edge of the Eta Corvi system seems like the proper environment for a reservoir of cometary bodies.
Team member Jessica Agarwal (European Space Agency) says the 100,000 tons of ejected material is mostly millimeters to centimeters in size, far coarser than the usual cometary fluff.
Brightening is often a sign of a cometary breakup, which exposes new surfaces to sunlight and vents trapped ice and gas that are then illuminated by the sun.
"Huge amounts of cometary bodies would have collided with outer icy satellites, including Titan," New Scientist quoted Yasuhito Sekine of the University of Tokyo, Japan, as saying.