Planetvorming

Planetvorming, also known as planetogenese, is the process by which planets form. This occurs in protoplanetary disks, which are rotating disks of dense gas and dust surrounding young stars. The prevailing theory for planet formation is the nebular hypothesis, which suggests that planets form from the accretion of material within these disks.

Initially, dust grains in the protoplanetary disk collide and stick together through electrostatic forces, forming larger aggregates. As these aggregates grow, gravity becomes increasingly important, pulling more material together. These growing clumps are called planetesimals, which can range in size from a few meters to hundreds of kilometers.

Through continued collisions and gravitational attraction, planetesimals merge to form larger bodies called protoplanets. These protoplanets continue to accrete gas and dust, and in the inner, hotter regions of the disk, they primarily accumulate rocky and metallic materials, leading to the formation of terrestrial planets. In the outer, colder regions of the disk, protoplanets can grow massive enough to gravitationally capture large amounts of gas, primarily hydrogen and helium, forming gas giants.

The process of planet formation is not always smooth. Collisions can also lead to the fragmentation of bodies. Over millions of years, the protoplanetary disk gradually dissipates as material is incorporated into planets, ejected from the system, or settles onto the star. The final stage involves orbital clearing, where planets gravitationally dominate their orbital regions, either accreting remaining debris or flinging it away.