Fig. 2: Polarimetric spectral gradients (PSG) of comets 2I/Borisov and Hale-Bopp.
From: Unusual polarimetric properties for interstellar comet 2I/Borisov
For 2I/Borisov we used λ1 = 557 nm, λ2 = 655 nm (red solid circles) and λ1 = 655 nm, λ2 = 768 nm (red solid squares); for comet Hale-Bopp38 we used λ1 = 484.5 nm, λ2 = 620 nm (blue empty circles) and λ1 = 670 nm, λ2 = 730 nm (blue empty squares). Error bars represent 1σ uncertainties, and are calculated from simple propagation of the polarimetric uncertainties that are estimated as explained in Methods subsection Polarimetry. We note that at phase angles values ≤21∘ the polarisation is directed along the scattering plane, at phase angle ≥21∘ it is directed along the perpendicular to the scattering plane.
