context: The formation of the ice giants, Neptune and Uranus, has proven difficult to model precisely. Current models suggest that the matter density in the outer regions of the Solar System was too low to account for the formation of such large bodies from the traditionally accepted method of core accretion, and various hypotheses have been advanced to explain their formation. One is that the ice giants were not formed by core accretion but from instabilities within the original protoplanetary disc and later had their atmospheres blasted away by radiation from a nearby massive OB star.
question: నెప్ట్యూన్ అసలు ప్రోటోప్లానెటరీ డిస్క్లో అస్థిరతల నుండి ఏర్పడితే, అది దేనితో ఏర్పడలేదు?
answers: core accretion