planetesimal
/ˌplænɪˈtɛsɪməl/
noun
- A small, solid object in space that formed early in the solar system and can combine with others to make planets.
- Asteroids are leftover planetesimals from the early solar system.
- The spacecraft flew close to a large planetesimal to study its rocky surface.
- Scientists think that planetesimals clumped together to form Earth and the other planets.