Planet formation

Planet formation is the development of planets from gas and dust in disks surrounding young stars. It involves the growth of solid bodies and, for some planets, the capture of surrounding gas.

Protoplanetary disk: A disk of gas and dust surrounding a young star, where planets can form. Planet formation begins within this rotating reservoir of material.
Interstellar medium: The gas and dust between stars, from which stars and their surrounding disks form. Its material supplies the raw ingredients inherited by planet-forming disks.
Solar System formation: The formation of the Sun and its planets from a collapsing cloud and a surrounding disk about 4.6 billion years ago. The Solar System provides the best-studied record of planet formation.
Planetary migration: The change in a planet’s orbit caused by gravitational interactions with a disk or other bodies. Migration can reshape planetary systems while their disks are still present.
Dust coagulation: The sticking and growth of dust grains through collisions in a gas-rich environment. It starts the conversion of disk dust into larger solid bodies.
Protoplanetary disk accretion: The inward flow of gas and solids through a disk onto a young star. Accretion changes how much material remains available for planets to grow.
HL Tauri: A young star in the Taurus star-forming region surrounded by a prominent disk with rings and gaps. Its disk image sparked discussion about how early structure relates to planet growth.
Disk dispersal: The removal of gas and dust from a young star’s circumstellar disk. Its timing sets a deadline for gas accretion and disk-driven migration.
Planetesimal: A solid body, typically kilometers across, that can grow through collisions and gravity. Planetesimals are the intermediate building blocks between dust and planetary embryos.
Snow line: The disk radius beyond which water vapor can condense into ice under local conditions. The extra solid material beyond it favors the growth of large planetary cores.

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