protoplanet

noun

pro·​to·​plan·​et ˈprō-tō-ˌpla-nət 

: 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

ˌprō-tō-ˈpla-nə-ˌter-ē 

adjective

Examples of protoplanet in a Sentence

Recent Examples on the Web

This is the first time the carbon and oxygen compositions of a birthing star, the natal disc, and a protoplanet were compared using a technique Wang and his colleagues had developed earlier to isolate the light from just the disc and the planet. —Paul Smaglik, Discover Magazine, 18 Dec. 2024

The combination of these unique features allowed scientists to observe the transiting protoplanet. —Julia Jacobo, ABC News, 20 Nov. 2024

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

Word History

First Known Use

1949, in the meaning defined above

Kids Definition

protoplanet

noun

pro·​to·​plan·​et ˈprōt-ō-ˌplan-ət 

: a whirling mass of gas that rotates around a star and is believed to become a planet

protoplanetary

ˌprōt-ō-ˈplan-ə-ˌter-ē 

adjective