Before all the planets migrated in our solar system, it looked very different from the way it does today. The sun would have been surrounded by a protoplanetary disk, which was made up of gas, dust, and small particles of rock and ice. The disk was very hot near the sun and cooler farther away.

The planets formed from the protoplanetary disk by a process called accretion. As the small particles in the disk collided with each other, they began to stick together and form larger and larger objects. The largest of these objects eventually became the planets.

As the planets grew larger, they began to move around the sun in their current orbits. However, the orbits of the planets were not always stable. Some planets moved closer to the sun while others moved farther away. This process is called planetary migration.

Planetary migration is thought to have occurred for several reasons. One reason is the presence of gas in the protoplanetary disk. The gas exerted a drag force on the planets, which caused them to lose energy and spiral closer to the sun. Another reason for planetary migration is the gravitational interactions between the planets. As the planets moved around the sun, they exerted gravitational forces on each other. This caused some planets to change their orbits and move to new locations.

Eventually, the protoplanetary disk disappeared and the planets settled into their current orbits. This process took several hundred million years.