Pebble accretion

Pebble accretion is a planet-formation process in which small, drifting solids are captured by larger bodies through gas drag and gravity. It can build planetary cores faster than collisions among larger planetesimals.

Stokes number: A dimensionless measure of how strongly a particle couples to a surrounding gas. It predicts whether drifting pebbles can be deflected into a growing body's capture path.
Protoplanetary disk: A rotating disk of gas and dust surrounding a young star, from which planets form. Pebble accretion takes place within this gas-rich environment.
Planetesimal accretion: The growth of planetary bodies through collisions and mergers among planetesimals. It builds cores through solid-body impacts rather than drag-assisted capture of pebbles.
Jupiter's core: The dense central region of Jupiter, containing heavy elements mixed with surrounding hydrogen and helium. Pebble accretion has been proposed as a rapid way to build the core needed for Jupiter's early formation.
Anders Johansen: A planetary scientist known for theoretical work on planet formation, including pebble accretion and the streaming instability. His research helped develop and quantify pebble accretion as a planet-formation mechanism.
Hill radius: The region around an orbiting body where its gravity can dominate over a star's tidal influence. Pebbles entering this gravitational domain can be captured when gas drag removes orbital energy.
Dust coagulation: The growth of dust grains through sticking collisions. Coagulation produces the larger solids that can behave as pebbles.
Runaway accretion: A growth phase in which larger bodies gain mass faster than smaller bodies through gravitational focusing. It describes size-dependent planetesimal growth, unlike pebble capture's gas-mediated delivery.
Gas giant formation: The processes by which giant planets acquire massive gaseous envelopes around solid or enriched cores. Rapid pebble-fed core growth may help explain how giant planets begin accreting gas.
Martin Lambrechts: A planetary scientist whose work helped establish pebble accretion as a rapid route to planetary cores. His collaboration with Johansen developed influential models of pebble-fed core growth.

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