Page "Nebular hypothesis" Paragraph 27

According to the Solar Nebular Disk Model, rocky planets form in the inner part of the protoplanetary disk, within the snow line, where the temperature is high enough to prevent condensation of water ice and other substances into grains.

This results in coagulation of purely rocky grains and later in the formation of rocky planetesimals.

Such conditions are thought to exist in the inner 3 – 4 AU part of the disk of a sun-like star.