plan·e·tes·i·mal | \ˌpla-nə-ˈte-sə-məl, -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

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At the same time, Jupiter may have hurled material inward as well, crashing hydrogen-rich asteroids and planetary embryos, or planetesimals, into crowded young terrestrial planets. Nola Taylor Redd, Smithsonian, "How Jupiter May Have Gifted Early Earth With Water," 20 June 2018 Their first line of evidence that the space rock was a chunk of what was originally a large planetesimal came from the size of the diamonds themselves. Deborah Netburn,, "One of the solar system’s early planets didn’t survive, but its diamonds are now on Earth," 17 Apr. 2018 Enough grist to form a massive ring could have only been supplied billions of years ago, when the early solar system was chock full of planetesimals. Paul Voosen, Science | AAAS, "Saturn’s rings are a recent addition to the solar system, Cassini observations show," 12 Dec. 2017 In order for the theory to work, planetesimals had to be huge, and this family was one of the biggest. Andrew Wagner, Science | AAAS, "Watch ‘dark asteroids’ reveal secrets of the early solar system," 3 Aug. 2017 The largest of these planetesimals grow faster than the ones around them and swallow their neighbors to grow into proto-planets. Simon Lock, Scientific American Blog Network, "A New Theory of How the Moon Formed," 9 June 2017 Dwarf planets have been defined by the International Astronomical Union since 2006 as celestial bodies that are roundish like their larger cousins in the solar system, but which haven’t gobbled up all the other planetesimals near themselves. Alexis Madrigal, WIRED, "Dwarf-Planet Rebranding Contest," 11 Nov. 2009 Dust grains grew into pebbles, and pebbles became world-building planetesimals. Nathaniel Scharping, Discover Magazine, "Everything Worth Knowing About ... Asteroids," 26 June 2017 These are thought to be fragments of the cores of planetesimals that formed early in the Solar System's history. John Timmer, Ars Technica, "New study suggests Jupiter’s formation divided Solar System in two," 17 June 2017

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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The first known use of planetesimal was in 1903

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