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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
Based on WordNet 3.0, Farlex clipart collection. © 2003-2012 Princeton University, Farlex Inc.
References in periodicals archive ?
Instead, the scientists categorized it more generally as planetesimal, meaning that 'Oumuamua is likely "just a leftover remnant from another solar system's birth process," Meech said, like a giant boulder that at some point could have fused with other space rocks to form a planet but didn't.
According to the standard theory, the Earth is thought to have formed from the collision of small celestial bodies known as planetesimals. Since such bodies were poor in water, Earth's water must have been delivered either by a larger planetesimal or by a shower of smaller objects such as asteroids or comets.
According to the scientists, the "planetesimal" that they found is well deep into the white dwarf's gravitational well.
Among specific topics are the chemical classification of nearby active galaxies, the chemical variation in the Orion A cloud cores, highlighting the dynamical interaction between planets and planetesimal belts with ALMA, and Keplarian and infall motions around the late-phase protostar TMC-1A.
For a long time, since the planetesimal occurrence that eventually became the Earth, air suspensions included predominantly materials other than organic (mineral and rock particles) and low-molecular organic compounds drawn by meteorites and asteroids.
See was critical of the planetesimal hypothesis, as it was known, and in 1909 attacked it in terms that drew a sharp response from Moulton, implying amongst other things that See, one of his former teachers at Chicago, had plagiarised his work; a charge he reiterated with biting sarcasm in a 1912 February critique 'Capture theory and capture practice', published in Popular Astronomy.
Chamberlin a "planetesimal" mechanism for the origin of our solar system that temporarily replaced Laplace's nebular hypothesis, declared that astronomy "is a science" because "the facts which have been acquired by observations and experiments are classified on the basis of their essential relations to each other and to the facts and principles of other sciences." (30) This resembles Torrey's factual "analysis" followed by "synthesis." Moulton offered this characterization of scientific procedure in his 1906 astronomy textbook, which passed through several editions in the first quarter of the twentieth century.
Nevertheless, we have come to realize that these impacts not only contributed to forming our planet (through planetesimal collision and accretion), but also by modifying it through time, and even punctuating the path of life's evolution.
Two prominent examples of this process are planetesimal interactions with the gaseous component of the protoplanetary disk during the formation of the solar system and orbital decay of ring particles as a result of drag caused by extended planetary atmospheres.
The iron and nickel rich planetesimal survived a system-wide cataclysm that followed the death of its host star, SDSS J122859.93+104032.9.