New Space and Tech

The Interstellar Interlopers

By Keith Cowing
Status Report
September 22, 2022
Filed under , , , , ,
The Interstellar Interlopers
The trajectory of 1I/‘Oumuamua near perihelion, from 2017 August to December. The positions of the Earth and ‘Oumuamua at discovery on October 17 are indicated. Even black points indicate the positions of the Earth and ‘Oumuamua at time intervals of one month. Arrows indicate the directions of motion of both objects through their orbits.

Interstellar interlopers are bodies formed outside of the solar system but observed passing through it. The first two identified interlopers, 1I/`Oumuamua and 2I/Borisov, exhibited unexpectedly different physical properties.

1I/`Oumuamua appeared unresolved and asteroid-like whereas 2I/Borisov was a more comet-like source of both gas and dust. Both objects moved under the action of non-gravitational acceleration. These interlopers and their divergent properties provide our only window so far onto an enormous and previously unknown galactic population. The number density of such objects is ∼ 0.1 AU−3 which, if uniform across the galactic disk, would imply 1025 to 1026 similar objects in the Milky Way.

The interlopers likely formed in, and were ejected from, the protoplanetary disks of young stars. However, we currently possess too little data to firmly reject other explanations.

David Jewitt, Darryl Z. Seligman

Comments: 40 pages, 19 figures, 7 tables, invited review in ARA&A Volume 61, submitted, comments welcome
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2209.08182 [astro-ph.EP] (or arXiv:2209.08182v1 [astro-ph.EP] for this version)
Submission history
From: Darryl Seligman
[v1] Fri, 16 Sep 2022 22:08:36 UTC (2,665 KB)

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