  The discovery of the first interstellar object passing through the Solar
System, 1I/2017 U1 ('Oumuamua), provoked intense and continuing interest from
the scientific community and the general public. The faintness of 'Oumuamua,
together with the limited time window within which observations were possible,
constrained the information available on its dynamics and physical state. Here
we review our knowledge and find that in all cases the observations are
consistent with a purely natural origin for 'Oumuamua. We discuss how the
observed characteristics of 'Oumuamua are explained by our extensive knowledge
of natural minor bodies in our Solar System and our current knowledge of the
evolution of planetary systems. We highlight several areas requiring further
investigation.
