  We investigate the trapping of interstellar objects during the early stages
of star and planet formation. Our results show a very wide range of possible
values that will be narrowed down as the population of interstellar objects
becomes better characterized. When assuming a background number density of
2$\cdot$10$^{15}$ pc$^{-3}$ (based on 1I/'Oumuamua detection), a velocity
dispersion of 30 km/s and an equilibrium size distribution, the number of
interstellar objects captured by a molecular cloud and expected to be
incorporated to each protoplanetary disk during its formation is O(10$^{9}$)
(50 cm-5 m), O(10$^{5}$) (5 m-50 m), O(10$^{2}$) (50 m-500 m), O(10$^{-2}$)
(500 m-5 km). After the disk formed, the number of interstellar objects it
could capture from the ISM during its lifetime is 6$\cdot$10$^{11}$ (50 cm-5
m), 2$\cdot$10$^{8}$ (5 m-50 m), 6$\cdot$10$^{4}$ (50 m-500 m), 20 (500 m-5
km); in an open cluster where 1% of stars have undergone planet formation,
these values increase by a factor of O(10$^{2}$-10$^{3}$). These trapped
interstellar objects might be large enough to rapidly grow into larger
planetesimals via the direct accretion of the sub-cm sized dust grains in the
protoplanetary disk before they drift in due to gas drag, helping overcome the
meter-size barrier, acting as "seeds" for planet formation. They should be
considered in future star and planet formation models and in the potential
spread of biological material across the Galaxy.

Earth and Planetary Astrophysics;Astrophysics of Galaxies;Solar and Stellar Astrophysics