planeettakehitystä

Planet development, known in Finnish as planeettakehitys, refers to the process by which a planetary body forms and evolves from the surrounding material of a protoplanetary disk. The process typically begins with the gravitational collapse of a cloud of gas and dust around a young star, resulting in a rotating disk. Within this disk, microscopic dust grains stick together through electrostatic forces, gradually building larger aggregates. Over time, these aggregates grow into planetesimals—kilometer‑sized bodies that can gravitationally attract each other.

Accretion continues as planetesimals collide and merge, a process that can span millions of years. During this phase, the bodies heat up due to kinetic energy from impacts and decay of short‑lived radionuclides. If a protoplanet reaches a critical mass, its gravity can hold a gaseous envelope, leading to the formation of gas giants, or it can undergo differentiation where heavier elements sink toward the core while lighter materials rise, creating layered structures such as cores, mantles, and crusts.

In the later stages, dynamical interactions—such as orbital resonances, collisions, and gravitational scattering—shape the final planetary system architecture. Planetary migration, driven by interactions with the disk gas or remaining planetesimals, can move forming planets inward or outward, influencing the composition and habitability of environments. The study of planet development combines observational astronomy, theoretical models, and numerical simulations, providing insights into the origins of our Solar System and the diversity of exoplanetary systems found throughout the galaxy.