  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.
