planetesimal hypothesis

UK: /ˌplænɪˈtɛsɪməl/

Collins Concise English Dictionary © HarperCollins Publishers::

planetesimal hypothesis noun

1. the discredited theory that the close passage of a star to the sun caused many small bodies to be drawn from the sun, eventually coalescing to form the planets

WordReference Random House Unabridged Dictionary of American English © 2025

plan•e•tes•i•mal  (plan′i tes′ə məl), [Astron.]
n. 

1. Astronomy one of the small celestial bodies that, according to one theory (planetes′imal hypoth′esis), were fused together to form the planets of the solar system.

adj. 

2. Astronomy of or pertaining to a planetesimal or planetesimals.

• planet + (infinit)esimal 1900–05