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Unusual polarimetric properties for interstellar comet 2I/Borisov

2021; Nature Portfolio; Volume: 12; Issue: 1 Linguagem: Inglês

10.1038/s41467-021-22000-x

2041-1723

S. Bagnulo, A. Cellino, L. Kolokolova, Rok Nežić, T. Santana-Ros, G. Borisov, A. A. Christou, Philippe Bendjoya, M. Devogèle,

Planetary Science and Exploration

So far, only two interstellar objects have been observed within our Solar System. While the first one, 1I/'Oumuamua, had asteroidal characteristics, the second one, 2I/Borisov, showed clear evidence of cometary activity. We performed polarimetric observations of comet 2I/Borisov using the European Southern Observatory Very Large Telescope to derive the physical characteristics of its coma dust particles. Here we show that the polarization of 2I/Borisov is higher than what is typically measured for Solar System comets. This feature distinguishes 2I/Borisov from dynamically evolved objects such as Jupiter-family and all short- and long-period comets in our Solar System. The only object with similar polarimetric properties as 2I/Borisov is comet C/1995 O1 (Hale-Bopp), an object that is believed to have approached the Sun only once before its apparition in 1997. Unlike Hale-Bopp and many other comets, though, comet 2I/Borisov shows a polarimetrically homogeneous coma, suggesting that it is an even more pristine object.