plan·​e·​tes·​i·​mal | \ ˌpla-nə-ˈte-sə-məl How to pronounce planetesimal (audio) , -zə-məl \

Definition of planetesimal

: any of numerous small celestial bodies that may have existed at an early stage of the development of the solar system

Examples of planetesimal in a Sentence

Recent Examples on the Web The most massive objects in the disk are called planetesimals, and their locations are shaped by interactions with other planets in the system. Meredith A. Macgregor, Scientific American, "Astronomers Watch as Planets Are Born," 19 May 2020 In the case of Mars, two different planetesimals with very different water content could have collided and never fully mixed, the researchers said. Ashley Strickland, CNN, "Meteorites reveal that Martian water came from different sources," 30 Mar. 2020 The timing would be fortuitous, given the mounting detections of individual planetesimals outside of the Solar System. Jennifer Ouellette, Ars Technica, "Study: ‘Oumuamua interstellar object might be remnant of a “super-Earth”," 14 Apr. 2020 Its uniform color, smooth surface and how the lobes came together help piece together a picture of how the planetesimal came to be. Ashley Strickland, CNN, "Distant object in our solar system could show how planets form, scientists reveal," 13 Feb. 2020 Except there seems to be a crucial bottleneck in this planetary assembly line: the jump from pebbles to kilometer-scale building blocks called planetesimals. Lee Billings, Scientific American, "New Horizons May Have Solved Planet Formation Cold Case," 20 Feb. 2020 Studying Arrokoth can shed light on how the building blocks of planets, called planetesimals, formed in our solar system. Ashley Strickland, CNN, "Distant object in our solar system could show how planets form, scientists reveal," 13 Feb. 2020 If this planetesimal was once Earth-like, as Manser believes, the outcome is bleak. Catherine Zuckerman, National Geographic, "Newfound tiny planet may be a glimpse of Earth's ultimate fate," 4 Apr. 2019 As the story goes, Mercury suffered a stupendous collision near the end of the period of planetary accretion, struck by a planetesimal so big that much of its crust was blasted into space. Kim Stanley Robinson, National Geographic, "Dear MESSENGER: How unmasking Mercury brought art to life," 22 Mar. 2019

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'planetesimal.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of planetesimal

1903, in the meaning defined above

History and Etymology for planetesimal

planet + -esimal (as in infinitesimal)

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Time Traveler for planetesimal

Time Traveler

The first known use of planetesimal was in 1903

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Last Updated

8 Jun 2020

Cite this Entry

“Planetesimal.” Dictionary, Merriam-Webster, Accessed 11 Jul. 2020.

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Rhyming Dictionary: Words that rhyme with planetesimal Encyclopedia article about planetesimal

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