He awa whiria: the tidal streams of interstellar objects

TL;DR

This paper models the distribution and properties of interstellar object streams in the Galaxy, predicting that the Sun encounters millions of such streams, with some potentially traceable to their parent stars or clusters.

Contribution

It introduces a simulation framework for ISO streams in the Galaxy and predicts their properties and encounter rates with the Solar System.

Findings

The Sun may encounter over a million ISO streams.

Most ISOs are not traceable to their parent stars.

ISO streams from the same origin are younger and colder.

Abstract

Upcoming surveys are likely to discover a new sample of interstellar objects (ISOs) within the Solar System, but questions remain about the origin and distribution of this population within the Galaxy. ISOs are ejected from their host systems with a range of velocities, spreading out into tidal streams - analogous to the stellar streams routinely observed from the disruption of star clusters and dwarf galaxies. We create a simulation of ISO streams orbiting in the Galaxy, deriving a simple model for their density distribution over time. We then construct a population model to predict the properties of the streams in which the Sun is currently embedded. We find that the number of streams encountered by the Sun is quite large, ~ 10^6 or more. However, the wide range of stream properties means that for reasonable future samples of ISOs observed in the Solar System, we may see ISOs from the same star ("siblings"), and we are likely to see ISOs from the same star cluster ("cousins"). We also find that ISOs are typically not traceable to their parent star, though this may be possible for ISO siblings. Any ISOs observed with a common origin will come from younger, dynamically colder streams.