any of a number of small bodies formerly thought to have been drawn from the sun by the close passage of a star to the sun, eventually coalescing to form the planets
an icy planetesimal
adjective
2.
of or relating to planetesimals
planetesimal theory/hypothesis/size
Word origin
C20: from planet + infinitesimal
planetesimal in American English
(ˌplænəˈtɛsɪməl; ˌplænətɛzɪməl)
noun
in various theories about the origin of the solar system, any of the small, cold masses of rock or ice that merged to form a planet