planetesimal

Any of innumerable small bodies thought to have orbited the sun during the formation of the planets.

Of or pertaining to a minute planet or planetary body.

One of the minute bodies moving in planetary orbits, from time to time overtaking each other and coalescing, and so gradually building up the planets, according to the planetesimal hypothesis.

Any of many small, solid astronomical objects, that orbit a star and form protoplanets through mutual gravitational attraction

one of many small solid celestial bodies thought to have existed at an early stage in the development of the solar system