Discerning between Different ’Oumuamua Models by Optical and Infrared Observations

The first interstellar object to be observed in our solar system, 1I/2017 U1 'Oumuamua, combines the lack of observable cometary activity with an extra-gravitational acceleration. This has given rise to several mutually exclusive explanations based on different assumptions in the material composition of 'Oumuamua. We show how a combination of observations in the infrared and optical spectra may serve to distinguish between these explanations once another object with 'Omuamua-like properties comes close enough to Earth. This possibility is linked to the widely different thermal properties of the different material models that have been proposed. Developing a model for the thermal conduction and infrared signal from a fractal model, we compare predictions of the infrared signal with that from standard thermal models that assume 'Oumuamua to be either a solid piece of rock/ice or a thin sheet.