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

Early in the history of the solar system, a massive protoplanet plowed into a young Earth. —Nola Taylor Tillman, Space.com, 8 May 2025

The results allowed for a first-of-its-kind systemic study of the 3D structures of multiple protoplanet disks. —Andrew Paul, Popular Science, 30 Apr. 2025

According to the leading Giant Impact Hypothesis, a Mars-sized protoplanet called Theia delivered the one impact to rule them all. —Max Bennett, Discover Magazine, 12 Apr. 2025

The observation of these protoplanets is a remarkable achievement for MagAO-X, which is an adaptive optics system. —Robert Lea, Space.com, 22 Mar. 2025

Word History

First Known Use

1949, in the meaning defined above

Rhymes for protoplanet

• pomegranate
• gannet
• granite
• planet
• intranet

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