Earth & SkyGreek → English
Protoplanet
/ˈproʊtoʊˌplænɪt/noun
A large body in a young star system that has swept up much of its orbital zone but is not yet a finished planet.
The Greek roots
πρῶτος
prôtos
first, foremost
πλανήτης
planḗtēs
wanderer
Literally: “first planet”
The story of the word
Mid-twentieth-century coinage for the stage between planetesimal and planet. The most famous protoplanet never got to be one: the giant-impact hypothesis has a Mars-sized body, usually called Theia, striking the young Earth and throwing off the debris that became the Moon. πρῶτος does the same job across English science, marking the earliest or the original, in protozoa, prototype and protein, which Berzelius named as the substance of first importance.
- How it travelled
- Ancient Greek → scientific coinage → English
- First recorded
- 20th century
Same family
prototypeproteinprotocolplanet
In a sentence
Vesta is close enough to intact that geologists treat it as a surviving protoplanet.