The protostar heats the inner part of the disk (1500^o K) while the outer portions remain cold (50^o K). Different elements condense from the gas to solid phase according to the local temperature: silicate and iron compounds only condense in the inner disk while these plus ices (water, methane, nitrogen) can condense in the outer disk.

The planetessimals in the inner disk end up as rocky objects while those in the outer disk are a mixture of rock and ice.

The largest planets form at intermediate distances from the star because of the relatively high density and large volume for accretion. These planets are so massive that they also accrete much of the gas in the disk.

What disk gas that is not captured by the giant planets is finally blown out of the system by flarings in the young star (the T Tauri stage).

The resulting system has inner, TERRESTRIAL planets (rocky) and outer, JOVIAN (or gas giant) planets (with rocky and icy cores surrounded by thick gas envelopes).