nebular hypothesis

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A hypothesis concerning the formation of stars and planets, and therefore the origin of the solar system, according to which a rotating nebula underwent gravitational collapse into a star with an accretion disk, from which planets condensed or formed by coagulation of dust particles into increasingly larger bodies.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun (cosmology) the theory that the solar system evolved from a hot gaseous nebula