protoplaneettilevyestä

A protoplanetary disk is a torus-shaped cloud of gas and dust surrounding a young star. These disks are crucial to the process of planet formation. Within the disk, material gradually clumps together through accretion. Initially, dust grains collide and stick, forming larger aggregates. These aggregates then grow into planetesimals, which are kilometer-sized bodies. As planetesimals continue to collide and merge, they eventually form protoplanets, the embryonic stages of planets. The composition and structure of the protoplanetary disk influence the types of planets that form. Regions closer to the star tend to be hotter, allowing only rocky materials to condense, leading to the formation of terrestrial planets. Further out, in colder regions, ices can also form, enabling the accretion of large amounts of gas to create gas giants and ice giants. The lifetime of a protoplanetary disk is typically a few million years, after which the material either accretes onto forming planets, is ejected from the system, or is dispersed by the stellar wind of the central star. Studying these disks provides invaluable insights into the early stages of planetary system evolution.