planetesimal
noun
plan·e·tes·i·mal
ˌpla-nə-ˈte-sə-məl 
-zə-məl
: any of numerous small celestial bodies that may have existed at an early stage of the development of the solar system
Examples of planetesimal in a Sentence
Recent Examples on the Web
As detailed in a study published today in the journal Science, researchers describe the aftermath of two separate collisions between two small, rocky cosmic objects called planetesimals.
—
Andrew Paul, Popular Science, 18 Dec. 2025
However, debris disks fade as collisions become less frequent and dust is gradually removed — either because it's blown out by stellar radiation, swept up by planets or remaining planetesimals or has fallen into the central star.
—Samantha Mathewson, Space.com, 5 Dec. 2025
But scientists have always known that the first solid parts of planets, known as planetesimals, must form much earlier.
—Eric Lagatta, USA Today, 18 July 2025
While astronomers have previously seen young discs that contain newborn, massive planets like Jupiter, it was not yet proven that the first solid parts of nascent planets, known as planetesimals, must form further back in time, at earlier stages, McClure said.
—Julia Jacobo, ABC News, 17 July 2025
See All Example Sentences for planetesimal
Examples are automatically compiled from online sources to
show current usage.
Read More
Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
Send us feedback.
Andrew Paul, Popular Science, 18 Dec. 2025
However, debris disks fade as collisions become less frequent and dust is gradually removed — either because it's blown out by stellar radiation, swept up by planets or remaining planetesimals or has fallen into the central star.
—Samantha Mathewson, Space.com, 5 Dec. 2025
But scientists have always known that the first solid parts of planets, known as planetesimals, must form much earlier.
—Eric Lagatta, USA Today, 18 July 2025
While astronomers have previously seen young discs that contain newborn, massive planets like Jupiter, it was not yet proven that the first solid parts of nascent planets, known as planetesimals, must form further back in time, at earlier stages, McClure said.
—Julia Jacobo, ABC News, 17 July 2025
See All Example Sentences for planetesimal
Cite this Entry
“Planetesimal.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/planetesimal. Accessed 26 Dec. 2025.
Copy CitationKids Definition
planetesimal
noun
plan·e·tes·i·mal
ˌplan-ə-ˈtes-ə-məl
-tez-
: one of numerous small solid heavenly bodies which may have existed at an early stage of the development of the solar system and from which the planets may have been formed
Love words? Need even more definitions?
Merriam-Webster unabridged
Share