Constraints on the Density and Internal Strength of 1I/'Oumuamua

TL;DR

This paper constrains the density and internal strength of 'Oumuamua using light curve data, suggesting it has a high aspect ratio and low cohesive strength, consistent with an interstellar origin.

Contribution

It provides the first detailed constraints on 'Oumuamua's density, shape, and internal strength based on photometric observations and modeling.

Findings

Density range 1500-2800 kg/m^3

Aspect ratio approximately 6:1

No significant cohesive strength needed

Abstract

1I/'Oumuamua was discovered by the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS 1) on 19 October 2017. Unlike all previously discovered minor planets this object was determined to have eccentricity $e > 1.0$, suggesting an interstellar origin. Since this discovery and within the limited window of opportunity, several photometric and spectroscopic studies of the object have been made. Using the measured light curve amplitudes and rotation periods we find that, under the assumption of a triaxial ellipsoid, a density range $1500 < \rho < 2800$ kg m$^{-3}$ matches the observations and no significant cohesive strength is required. We also determine that an aspect ratio of $6\pm 1:1$ is most likely after accounting for phase-angle effects and considering the potential effect of surface properties. This elongation is still remarkable but less than some other estimates.