protoplanet

noun

pro·​to·​plan·​et ˈprō-tō-ˌpla-nət How to pronounce protoplanet (audio)
: a hypothetical whirling gaseous mass within a giant cloud of gas and dust that rotates around a sun and is believed to give rise to a planet
protoplanetary adjective

Examples of protoplanet in a Sentence

Recent Examples on the Web The most popular theory says that about 4.5 billion years ago, a Mars-size protoplanet slammed into Earth. Kenneth Chang, New York Times, 1 Nov. 2023 But scientists have lacked smoking-gun evidence like a crater or pieces of the protoplanet, named Theia. Kenneth Chang, New York Times, 1 Nov. 2023 Further afield, one leading theory to account for certain quirks of our solar system’s architecture posits that early shifts in the orbits of Jupiter and Saturn sparked brutal cascades of collisions between nascent protoplanets. Lyndie Chiou, Scientific American, 25 Oct. 2023 The new measurements are significant as this is the first time water has been detected in a region where two or more protoplanets are known to exist. Jack Birle, Washington Examiner, 25 July 2023 See all Example Sentences for protoplanet 

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'protoplanet.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

First Known Use

1949, in the meaning defined above

Time Traveler
The first known use of protoplanet was in 1949

Dictionary Entries Near protoplanet

Cite this Entry

“Protoplanet.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/protoplanet. Accessed 5 Nov. 2024.

Kids Definition

protoplanet

noun
pro·​to·​plan·​et ˈprōt-ō-ˌplan-ət How to pronounce protoplanet (audio)
: a whirling mass of gas that rotates around a star and is believed to become a planet
protoplanetary adjective

More from Merriam-Webster on protoplanet

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