Protoplanet
In
cosmogony, a
protoplanet is a quasi-
planetoid which is slightly larger than a
planetesimal and orbits within a
solar nebula's protoplanetary discs. Such objects are formed by the
accretion of objects (such as
dust and planetesimals) within the
accretion disc of a
solar nebula. Early protoplanets are generally relatively
hot and
liquid. As the protoplanets cool into
planets, their heavier
elements will sink to the center; while lighter elements rise to the surface; such a process is known as
differentiation.
