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Related to Planetesimal theory: planetesimal hypothesis, Tidal theory, Nebular theory


Any of innumerable small bodies thought to have orbited the sun during the formation of the planets.

plan′e·tes′i·mal 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.


(ˌplænɪˈtɛsɪməl) astronomy
(Astronomy) any of a number of small bodies formerly thought to have been drawn from the sun by the close passage of a star to the sun, eventually coalescing to form the planets
(Astronomy) of or relating to planetesimals
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014


(ˌplæn ɪˈtɛs ə məl)
one of the small celestial bodies that, according to one theory, were fused to form the planets of the solar system.
[1900–05; planet + (infinit) esimal]
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.
ThesaurusAntonymsRelated WordsSynonymsLegend:
Noun1.planetesimal - one of many small solid celestial bodies thought to have existed at an early stage in the development of the solar system
celestial body, heavenly body - natural objects visible in the sky
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References in periodicals archive ?
Chamberlin had advanced the planetesimal theory (see 1905), which required a near collision that would draw out solar matter by gravitational pull and form the planets.