protoplanet

noun
pro·​to·​plan·​et | \ ˈprō-tō-ˌpla-nət How to pronounce protoplanet (audio) \

Definition of protoplanet

: 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

Other Words from protoplanet

protoplanetary \ ˌprō-​tō-​ˈpla-​nə-​ˌter-​ē How to pronounce protoplanet (audio) \ adjective

Examples of protoplanet in a Sentence

Recent Examples on the Web The protoplanet's star is estimated to be a relatively young 2 million years old, the same age at which our now 4.6 billion-year-old solar system saw planet formation. Wyatte Grantham-philips, USA TODAY, 5 Apr. 2022 In September, Morbidelli and his colleagues published an article in Nature Astronomy based on studies of the protoplanet Vesta that suggested how planetesimals would explain the current configuration of the solar system. Quanta Magazine, 3 Nov. 2021 Scientists have long agreed that the Moon formed when a protoplanet, called Theia, struck Earth in its infancy some 4.5 billion years ago. Paul Voosen, Science | AAAS, 23 Mar. 2021 Such a dry, large protoplanet would have separated into layers with an iron-depleted core and an iron-rich mantle, Desch says, some 2% to 3.5% denser than present-day Earth. Paul Voosen, Science | AAAS, 23 Mar. 2021 Such an event would have seen Jupiter absorb the protoplanet, which would have been 10 times Earth’s mass, causing their two dense cores to combine and diffuse after only 10 hours, as seen in the simulation above. Paul Voosen, Science | AAAS, 14 Aug. 2019 Scientific consensus about how the moon formed is that billions of years ago, a protoplanet crashed into Earth and the pieces of it revolved around the Earth to form the moon. Kristen Rogers, CNN, 22 Nov. 2019 Smaller objects, including Earth-sized protoplanets, would disintegrate in the atmosphere before reaching the core. John Timmer, Ars Technica, 14 Aug. 2019 One possible explanation is a cataclysmic head-on collision some 4.5 billion years ago between a young Jupiter and one of the many large protoplanets that likely populated the early solar system, planetary scientists report today in Nature. Paul Voosen, Science | AAAS, 14 Aug. 2019 See More

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

First Known Use of protoplanet

1949, in the meaning defined above

Learn More About protoplanet

Time Traveler for protoplanet

Time Traveler

The first known use of protoplanet was in 1949

See more words from the same year

Dictionary Entries Near protoplanet

protophyte

protoplanet

protoplasm

See More Nearby Entries 

Statistics for protoplanet

Cite this Entry

“Protoplanet.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/protoplanet. Accessed 25 Jun. 2022.

Style: MLA
MLACheck Mark Icon ChicagoCheck Mark Icon APACheck Mark Icon Merriam-WebsterCheck Mark Icon

More from Merriam-Webster on protoplanet

Britannica.com: Encyclopedia article about protoplanet

WORD OF THE DAY

Test Your Vocabulary

Great Words for Scrabble

  • scrabble tiles that read scrabble quiz
  • Which of the following Q-without-U words means the number five in cards or dice?
True or False

Test your knowledge - and maybe learn something along the way.

TAKE THE QUIZ
Universal Daily Crossword

A daily challenge for crossword fanatics.

TAKE THE QUIZ
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!