# High-Drag Interstellar Objects And Galactic Dynamical Streams

## TL;DR

This paper proposes that interstellar objects with low area density can be captured by gas drag in galactic streams, explaining 1I/'Oumuamua's properties and predicting a population of similar objects for future exploration.

## Contribution

It introduces the idea that gas drag in galactic streams can trap low-density interstellar objects, supporting the radiation pressure hypothesis for 1I's acceleration and enabling future detection strategies.

## Key findings

- Low area density explains 1I's kinematic association with the Pleiades stream.
- Gas drag can capture low-density interstellar objects in galactic streams.
- Targeted surveys can identify stream objects before perihelion for quick exploration.

## Abstract

The nature of 1I/'Oumuamua (henceforth, 1I), the first interstellar object known to pass through the solar system, remains mysterious. Feng \& Jones noted that the incoming 1I velocity vector "at infinity" ($\textbf{v}_{\infty}$) is close to the motion of the Pleiades dynamical stream (or Local Association), and suggested that 1I is a young object ejected from a star in that stream. Micheli $\textit{et al.}$ subsequently detected non-gravitational acceleration in the 1I trajectory; this acceleration would not be unusual in an active comet, but 1I observations failed to reveal any signs of activity. Bialy $\&$ Loeb hypothesized that the anomalous 1I acceleration was instead due to radiation pressure, which would require an extremely low mass-to-area ratio (or area density). Here I show that a low area density can also explain the very close kinematic association of 1I and the Pleiades stream, as it renders 1I subject to drag capture by interstellar gas clouds. This supports the radiation pressure hypothesis and suggests that there is a significant population of low area density ISOs in the Galaxy, leading, through gas drag, to enhanced ISO concentrations in the galactic dynamical streams. Any interstellar object entrained in a dynamical stream will have a predictable incoming $\textbf{v}_{\infty}$; targeted deep surveys using this information should be able to find dynamical stream objects months to as much as a year before their perihelion, providing the lead time needed for fast-response missions for the future $\textit{in situ}$ exploration of such objects.