Dix Planetary Science Seminar

Abstract: The first interstellar comet and only the second interstellar object
observed to enter the Solar System, 2I/Borisov, provides us an
unprecedented opportunity to study the physical characteristics of
comets around other stars relatively up close. We present results from
visible and near-infrared photometric and spectroscopic observations
of 2I taken from an ensemble of telescopes from conventional to
high-resolution observations. We find that 2I exhibits reddish to
neutral colors in the visible and NIR with a coma morphology and a
photometric lightcurve trend typical of distant Solar System comets
with activity being driven by super volatiles at distances exceeding 6
au and with a recent turn-on of H2O. Using the advanced capability to
significantly reduce the scattered light from the coma enabled by
high-resolution imaging, we estimate a diameter for 2I's nucleus of
<2-3 km, though the true diameter is likely 2-3 times smaller. We use
the size inferred for the first interstellar object, 1I/'Oumuamua, and
of 2I to roughly constrain the size distribution of interstellar
objects, and we comment on the galactic dynamics of these objects and
the prospects for where they came from in the Milky Way.