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[proh-toh-plan-it] /ˈproʊ toʊˌplæn ɪt/
noun, Astronomy
the collection of matter, in the process of condensation, from which a planet is formed.
1945-50; proto- + planet Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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British Dictionary definitions for protoplanet


a planet in its early stages of evolution by the process of accretion
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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Word Origin and History for protoplanet

1949, from proto- + planet.

Online Etymology Dictionary, © 2010 Douglas Harper
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Encyclopedia Article for protoplanet

in astronomical theory, a hypothetical eddy in a whirling cloud of gas or dust that becomes a planet by condensation during formation of a solar system. As the central body, or protostar, of the system contracts and heats up, the increasing pressure of its radiation is believed to drive off much of the thinner material of the protoplanets, particularly those closer to the nascent star

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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