Abstract
Abstract With the recent discoveries of interstellar objects Oumuamua and Borisov traversing the solar system, understanding the dynamics of interstellar objects is more pressing than ever. These detections have highlighted the possibility that captured interstellar material could be trapped in our solar system. The first step in rigorously investigating this question is to calculate a capture cross section for interstellar objects as a function of hyperbolic excess velocity, which can be convolved with any velocity dispersion to compute a capture rate. Although the cross section provides the first step toward calculating the mass of alien rocks residing in our solar system, we also need to know the lifetime of the captured objects. We use an ensemble of N-body simulations to characterize a dynamical lifetime for captured interstellar objects and determine the fraction of surviving objects as a function of time (since capture). We also illuminate the primary effects driving their secular evolution. Finally, we use the resulting dynamical lifetime function to estimate the current inventory of captured interstellar material in the solar system. We find that capture from the field yields a steady-state mass of only ∼10−13 M ⊕, whereas the mass remaining from capture events in the birth cluster is roughly 10−9 M ⊕.
Highlights
The recent discoveries of the irregular body Oumuamua (Meech et al 2017) and the comet Borisov (Jewitt & Luu 2019) have precipitated a boom in studies of interstellar objects
The objective of this paper is to examine the dynamical stability of captured interstellar objects and characterize their dynamical lifetime
We have examined the long-term stability of interstellar objects captured by our solar system
Summary
The recent discoveries of the irregular body Oumuamua (Meech et al 2017) and the comet Borisov (Jewitt & Luu 2019) have precipitated a boom in studies of interstellar objects. No objects present overwhelming evidence of having originated outside of our solar system (Morbidelli et al 2020). Given the complex dynamical architecture of the outer solar system, it is not straightforward to determine whether an object is of interstellar origin. A more severe difficulty is that we do not know the types of orbits on which such objects might reside. To address this issue, one must first determine the kinds of orbits onto which interstellar objects can be captured and determine which objects can survive for long enough to be considered quasi-permanent members of the solar system, rather than members of a transient population
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