# Dust bombardment can explain the extremely elongated shape of 1I/'Oumuamua and the lack of interstellar objects

## TL;DR

This paper proposes that interstellar dust bombardment can elongate small asteroids like 'Oumuamua over time, explaining its shape and the scarcity of observed interstellar objects.

## Contribution

It introduces a dust erosion model that accounts for the extreme elongation of 'Oumuamua and the limited number of interstellar objects observed.

## Key findings

- Dust bombardment can significantly elongate small asteroids over hundreds of millions of years.
- Interstellar objects are likely disrupted after tens of millions of years in the Galactic disk.
- The model explains the rarity and shape of 'Oumuamua and similar objects.

## Abstract

Asteroid 1I/'Oumuamua is the first observed interstellar object. Its light-curve amplitude indicates that the object is highly elongated with an axis ratio of at least 5:1. The absence of such elongated asteroids in the Solar system, as well as the apparent lack of observed interstellar objects, are intriguing problems. Here we show that 'Oumuamua may have originated as a slightly-elongated asteroid about $500\times300$ meters in size. Surface erosion, caused by interstellar dust bombardment, subsequently increased the axis ratio. Simply traveling through the interstellar medium for 0.03 to 2 Gyrs would have sufficed to give 1I its present shape. Passing through a 10 pc dust cloud with a grain density of $10^{-23} \ \mathrm{g/cm^3}$ at 50 km/s would have had a similar effect on 'Oumuamua's form. Smaller objects of around 100 meters in diameter can travel the Galactic disk for merely 30 Myrs before they are disrupted. This could explain the small number of interstellar objects observed to date.