What dictated the confinement of solid material to the inner region of the nebula?

Answer

The intensely hot temperatures near the protosun

Temperatures close to the Sun were so high that only the most refractory materials, like metals and silicates, could maintain a solid state and condense there.

What dictated the confinement of solid material to the inner region of the nebula?

#Videos

What Was The Composition Of The Solar Nebula? - Physics Frontier

Spaceastronomycompositionsolar systemsolar nebula