Kärnaccretion

Kärnaccretion is a hypothetical mechanism in planet formation theory that describes rapid growth of a protoplanetary core through focused accretion of dense solid material in localized disk regions. The term is not part of the standard core-accretion framework and is primarily discussed in speculative or theoretical contexts as a possible variant or complement to established models.

Proposed mechanisms for Kärnaccretion involve concentration of solids in disk substructures such as pressure maxima or vortices, where aerodynamic drag and drift of pebbles lead to enhanced solid flux onto an embryonic core. In these regions, increased relative velocities and gravitational focusing can accelerate mass buildup, potentially allowing a core to reach a critical size more quickly than in classical scenarios. Gas dynamics, disk temperature, and the presence of resonant traps may further influence efficiency and outcome, including the onset of envelope accretion around the growing core.

Status and implications: If operative, Kärnaccretion could shorten planet-formation timescales and affect the resulting planetary architecture, including the distribution of terrestrial and gas-rich planets. However, it remains unproven, and there is no direct observational confirmation. Current data from protoplanetary disks and exoplanet demographics have not definitively demonstrated the need for or existence of this mechanism; most work continues to test its viability within broader models of disk evolution and solid-body dynamics.

See also: Core accretion, Pebble accretion, Protoplanetary disk, Planet formation theory.