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

• Published in: Monthly notices of the Royal Astronomical Society. Letters 2019-03, Vol.484 (1), p.L75-L78
• Main Authors: Vavilov, Dmitrii E, Medvedev, Yurii D
• Format: Article
• Language: English
• ISSN: 1745-3925; 1745-3933
• DOI: 10.1093/mnrasl/sly244

ABSTRACT Asteroid 1I/’Oumuamua is the first observed interstellar object. Its light-curve amplitude indicates that the object is highly elongated with an axial ratio of at least 5:1. The absence of such elongated asteroids in the Solar system and 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 × 300 m in size. Surface erosion, caused by interstellar dust bombardment, subsequently increased the axial ratio. Simply travelling through the interstellar medium for 0.03 to 2 Gyr would have sufficed to give 1I its present shape. Passing through a 10 pc dust cloud with a grain density of 10−23 g cm−3 at 50 km s−1 would have had a similar effect on ’Oumuamua’s form. Smaller objects of around 100 m in diameter can travel the Galactic disc for merely 30 Myr before they are disrupted. This could explain the small number of interstellar objects observed to date.