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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.


(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


(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]
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
References in periodicals archive ?
Since the star's light exerts radiation pressure that would easily blow such small grains out of orbit, any dust near the star must have arrived there recently, perhaps from a swarm of comets, asteroids, or a dusty planetesimal.
While we don't know the cause of the tumbling, we predict that it was most likely sent tumbling by an impact with another planetesimal in its system, before it was ejected into interstellar space.
Dust trapping is one potential solution to a major stumbling block in our theories of how planets form, which predicts that particles should drift into the central star and be destroyed before they have time to grow to planetesimal sizes.
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.
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.
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.
Poco despues, en terminos astronomicos, hace 4 mil 450 o 4 mil 460 millones de anos, la Tierra sufrio otra colision, en esa ocasion fue contra un planetesimal muy grande.
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.
Ward has also contributed fundamental insights to humankind's understanding of planetesimal formation, the dynamical evolution of the moon, planet migration, planetary spin axis orientations, and the formation of planetary and satellite systems.
The resulting paper, "Identification of a primordial asteroid family constrains the original planetesimal population," appears in the August 3, 2017, online edition of Science.
Antarctic Meteorite Program (a collaboration among Cassidy, NASA, the National Science Foundation, and the Smithsonian Institution), as well as current field and curatorial practices, the nebular and planetesimal history of our solar system through key specimens, the significance of key samples from larger bodies, and much more.