Interstellar planetesimals: potential seeds for planet formation?. (arXiv:2110.15366v1 [astro-ph.EP])

<a href="http://arxiv.org/find/astro-ph/1/au:+Moro_Martin_A/0/1/0/all/0/1">Amaya Moro-Martín</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Norman_C/0/1/0/all/0/1">Colin Norman</a>

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.

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.

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