Year: 2026
Type: article
Abstract: ABSTRACT Planet formation requires growth over 12 orders of magnitude in size, from micron-sized dust grains to fully formed planets. The formation of $\sim \rm km$-sized planetesimals is the most challenging stage, where radial drift and fragmentation rapidly remove meter-sized solids from the protoplanetary disc. Overcoming this barrier requires favourable conditions for streaming instability to concentrate solids. These problems are exacerbated in binary star systems, where gravitational perturbations and disc truncation reduce the efficiency of planetesimal formation pathways. Planetesimal capture provides an alternative mechanism where unbound planetesimals are captured by the protoplanetary disc through gas drag, potentially bypassing the most restrictive growth stages. We investigate this process in circumstellar and circumbinary discs using over $3\times 10^7$ numerical experiments across a range of binary separations. For circumstellar discs, capture of large ($\gtrsim 50$ m) planetesimals is suppressed below $\sim 50$ au, with the strongest reduction at $\sim 10$ au, broadly consistent with the observed decrease in planet occurrence in binaries. Tight ($\sim 10\ \rm au$) binaries can still capture $\mathcal {O}(1)$ km-sized planetesimals, increasing to $\mathcal {O}(10)$ km-sized in wider systems during the birth cluster’s lifetime. Circumbinary discs are much less efficient, with capture rates dropping to $\sim 1 {{\ \rm per\ cent}}$ of the single-star case for binaries above $\sim 1$ au and becoming negligible for large planetesimals at wider separations. Overall, planetesimal capture provides a supplementary channel for delivering solids to binary systems and mitigating inefficiencies in in situ planetesimal formation.
Authors: Alia Pollard, Evgeni Grishin
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,046
OpenAlex ID: W7221333812