# Capture of free-floating planets by stellar systems

## TL;DR

This study uses 3D simulations to analyze how free-floating planets can be captured by stars, estimating a 1% capture rate and proposing factors that could increase this likelihood.

## Contribution

The paper introduces a new simulation framework and analytical model to estimate free-floating planet capture rates by stars, highlighting the potential for higher capture probabilities.

## Key findings

- Approximately 1% of stars may temporarily capture free-floating planets.
- The capture cross section depends on mass, impact parameters, and velocities.
- Additional physical processes could further increase capture likelihood.

## Abstract

Evidence of exoplanets with orbits that are misaligned with the spin of the host star may suggest that not all bound planets were born in the protoplanetary disk of their current planetary system. Observations have shown that free-floating Jupiter-mass objects can exceed the number of stars in our galaxy, implying that capture scenarios may not be so rare. To address this issue, we construct a three-dimensional simulation of a three-body scattering between a free-floating planet and a star accompanied by a Jupiter-mass bound planet. We distinguish between three different possible scattering outcomes, where the free-floating planet may get captured after the interaction with the binary, remain unbound, or "kick-out" the bound planet and replace it. The simulation was performed for different masses of the free-floating planets and stars, as well as different impact parameters, inclination angles and approach velocities. The outcome statistics are used to construct an analytical approximation of the cross section for capturing a free-floating planet by fitting their dependence on the tested variables. The analytically approximated cross section is used to predict the capture rate for these kinds of objects, and to estimate that about 1\% of all stars are expected to experience a temporary capture of a free-floating planet during their lifetime. Finally, we propose additional physical processes that may increase the capture statistics and whose contribution should be considered in future simulations.