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The Dynamics of Interstellar Asteroids and Comets within the Galaxy: an Assessment of Local Candidate Source Regions for 1I/`Oumuamua and 2I/Borisov

Status Report From: arXiv.org e-Print archive
Posted: Thursday, November 7, 2019

Tim Hallatt, Paul Wiegert

(Submitted on 6 Nov 2019)

The speed of interstellar asteroid `Oumuamua with respect to the Local Standard of Rest of our Galaxy is low, implying it is young. With this as our hypothesis, we assess possible origin systems for this interstellar asteroid.

First,`Oumuamua's past trajectory is modelled under the influence of 'disk heating' (ie. gravitational scattering) to assess how far back one can trace its path. The stochastic nature of disk heating means that a back integration of `Oumuamua can only expect to be within 15 pc and 2 km/s at -10 Myr growing to 400 pc and 10 km/s at -100 Myr, sharply limiting our ability to determine a precise origin. However, we can show that `Oumuamua's origin system is likely currently within 1 kpc of Earth, within the local Orion Arm, and thus relatively accessible to telescopic study, if it can be identified.

Second, we perform a back-integration of `Oumuamua's trajectory to assess potential candidate regions. The Gaia DR2 and SIMBAD catalogs were considered, as were the Catalog of Suspected Nearby Young Stars (Riedel et al 2018) and moving groups as compiled in Gagne et al 2018. Though disk heating prevents making any but a statistical link to local star-forming regions and moving groups, `Oumuamua passed through at least a considerable subset of the Carina and Columba moving groups at a time comparable to their ages, making this perhaps the most plausible source region, if the asteroid was ejected by the planet-forming process.

During the writing of this paper a second interstellar comet, 2I/Borisov, was discovered. Though unlikely to be young due to its high speed with respect to the LSR, we performed a similar analysis and found three stars in the Ursa Major group, one brown dwarf, and 8 Gaia DR2 stars to have plausible encounters at speeds <30 km/s and within 2 pc. We do not find any plausible encounters at speeds lower than 13 km/s. [editted for length]

Comments: 24 pages, 3 figures. Submitted to AAS journals. Animated fly-throughs of 1I\Oumuamua and 2I\Borisov's approach through the Milky Way are available at this http URL

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA)

Cite as: arXiv:1911.02473 [astro-ph.EP] (or arXiv:1911.02473v1 [astro-ph.EP] for this version)

Submission history

From: Paul A. Wiegert 

[v1] Wed, 6 Nov 2019 16:44:13 UTC (826 KB)

https://arxiv.org/abs/1911.02473

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