Capture of interstellar objects during stellar encounters
Abstract
As they orbit within the Galaxy, stars swim through a vast population of interstellar objects (ISOs). In this paper, we use N -body simulations to show that a fraction of ISOs within ∼1 pc of the Sun (its tidal radius) may be captured during the flyby of another star – a mechanism that requires no planets. Capture is most efficient when the impulse imparted by the flyby is comparable to the escape speed at the widest stable orbit, which is roughly 0.1 km/s for the Sun. The ISO capture is dominated by the few highest-impulse stellar flybys, typically involving relatively slow encounters with massive stars. Most ISOs are captured in the outer parts of the Oort cloud, with semimajor axes greater than ∼50000 au. Using Monte Carlo simulations, we show that the Sun underwent only a small number of ISO-capturing flybys in its history (median [mean] of 1 [1.7]). Using the Ō tautahi-Oxford population model, we estimate that a few times ∼10 4 ‘Oumuamua-sized ISOs were likely captured by the Sun. This only represents a ∼10 −8±1 contribution to the total Oort cloud population, yet it contains roughly as many present-day captured ISOs as Jupiter-assisted capture provides. Given that flybys are unavoidable in the Galactic field, most stars should host sparse Oort clouds populated with ISOs captured during stellar flybys. Massive stars are both the main drivers of capture when they fly by a given star, and more efficient at capturing ISOs around themselves than low-mass stars.
Related
- Measuring the Age and Initial Composition of Interstellar Objects
- Near-infrared periodicity in the SPICY catalog. True young stellar objects versus contaminants
- Sky-Plane Velocity Distributions of Interstellar Objects and Implications for Their Detection
- Sky-plane velocity distributions of interstellar objects and implications for their detection
- Investigating the formation of small Solar System objects using stellar occultations by satellites: present, future and its use to update satellite orbits
BibTeX
@article{raymond2026capture,
title = {{Capture of interstellar objects during stellar encounters}},
author = {Sean N. Raymond and Nathan Kaib and Matthew Hopkins},
journal = {Astronomy \& Astrophysics - A\&A},
year = {2026},
month = aug,
doi = {10.1051/0004-6361/202660697},
url = {https://hal.science/hal-05760826v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Capture of interstellar objects during stellar encounters
AU - Sean N. Raymond
AU - Nathan Kaib
AU - Matthew Hopkins
PY - 2026
DA - 2026/08/24
JO - Astronomy & Astrophysics - A&A
DO - 10.1051/0004-6361/202660697
UR - https://hal.science/hal-05760826v1
AB - As they orbit within the Galaxy, stars swim through a vast population of interstellar objects (ISOs). In this paper, we use N -body simulations to show that a fraction of ISOs within ∼1 pc of the Sun (its tidal radius) may be captured during the flyby of another star – a mechanism that requires no planets. Capture is most efficient when the impulse imparted by the flyby is comparable to the escape speed at the widest stable orbit, which is roughly 0.1 km/s for the Sun. The ISO capture is dominated by the few highest-impulse stellar flybys, typically involving relatively slow encounters with massive stars. Most ISOs are captured in the outer parts of the Oort cloud, with semimajor axes greater than ∼50000 au. Using Monte Carlo simulations, we show that the Sun underwent only a small number of ISO-capturing flybys in its history (median [mean] of 1 [1.7]). Using the Ō tautahi-Oxford population model, we estimate that a few times ∼10 4 ‘Oumuamua-sized ISOs were likely captured by the Sun. This only represents a ∼10 −8±1 contribution to the total Oort cloud population, yet it contains roughly as many present-day captured ISOs as Jupiter-assisted capture provides. Given that flybys are unavoidable in the Galactic field, most stars should host sparse Oort clouds populated with ISOs captured during stellar flybys. Massive stars are both the main drivers of capture when they fly by a given star, and more efficient at capturing ISOs around themselves than low-mass stars.
SN - 0004-6361
SN - 1432-0746
ER -