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
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This suggests that the exoplanets' orbits may have changed over time following interactions with neighboring cosmic objects, such as gas, planetesimals or a companion star, bringing the inner planet, TOI-1453 b, into an orbit much closer to its host star.
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Samantha Mathewson, Space.com, 27 Mar. 2025
Another difference is that while regular moons emerged as their host planet was forming, many irregular moons are believed to have been planetesimals (small, early-stage planets) captured by their host planet at the end of its formation.
—Jack Knudson, Discover Magazine, 17 Mar. 2025
As these stars and planets whirl around each other, their gravitational interactions perturb the orbits of other smaller objects in Alpha Centauri, ranging from asteroids and comets — planetesimals left over from the formation of our neighboring system — to particles of dust.
—Robert Lea, Space.com, 5 Mar. 2025
In these follow-up simulations, a small star, about three quarters the mass of the sun, is birthed out of the dense gas with planetesimals—kilometer-scale precursors to terrestrial planets—in tow.
—Conor Feehly, Scientific American, 4 Mar. 2025
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Samantha Mathewson, Space.com, 27 Mar. 2025
Another difference is that while regular moons emerged as their host planet was forming, many irregular moons are believed to have been planetesimals (small, early-stage planets) captured by their host planet at the end of its formation.
—Jack Knudson, Discover Magazine, 17 Mar. 2025
As these stars and planets whirl around each other, their gravitational interactions perturb the orbits of other smaller objects in Alpha Centauri, ranging from asteroids and comets — planetesimals left over from the formation of our neighboring system — to particles of dust.
—Robert Lea, Space.com, 5 Mar. 2025
In these follow-up simulations, a small star, about three quarters the mass of the sun, is birthed out of the dense gas with planetesimals—kilometer-scale precursors to terrestrial planets—in tow.
—Conor Feehly, Scientific American, 4 Mar. 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 1 Apr. 2025.
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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
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