Planets · Comets and asteroids
Planetesimal
Say it: plan-ih-TESS-ih-mul IPA: /ˌplænɪˈtɛsɪməl/ noun
Planetesimal: A solid body formed in a young planetary system that can contribute to the growth of planets.
Young planetary systems contain material ranging from tiny grains to larger bodies. Planetesimals occupy an important stage in the assembly of rocky and icy worlds.
- Example
- Repeated collisions allowed some planetesimals to grow into larger planetary embryos.
- Why astronomers use it
- They connect primitive solar-system material with the formation of planets.
- Tiny cosmic connection
- Not every planetesimal became part of a planet; surviving small bodies can preserve clues to this earlier stage.
Observatory Planets Comets and asteroids
Where to check it
- NASA Science: Universe glossary (opens in a new tab)
- NASA Hubble glossary (opens in a new tab)
- Wikipedia: Planetesimal (opens in a new tab)
Written for Cool Moon Facts in its own words; the sources cover the same idea in more depth.