Solar Disc

As the Sun formed, gravity pulled the gas and dust around it into a spinning disc.

Here the dust grains hit each other and their sticky layers of ice stuck them together into bigger snowballs (scientific name planetesimals).

This made the disc break up into rings. Here the snowballs stuck together to make larger and larger lumps. The dust grains at the center of each snowball collected into rocky lumps.

Finally gravity collected these rocky lumps together until they formed planets