Dependence of the particle size on parameter of the polarization maximum (P_max ). The filled circles indicate size-sorted carbon samples (Hadamcik et al. 2009). The filled squares and filled triangles denote two size-sorted carbonaceous chondrites (e.g., Orgueil and Allende meteorites, Worms et al. 2000; Hadamcik et al. 2011), respectively. The 3 μm and 160 μm lines are qualified from the Itokawa sample limits. The 63 μm line originates from the spectral resemblance of the heated Murchison meteorite (Sect. 4.1). The P_max values of 1998 KU₂ correspond to the lower limit from our observation (solid line) and the estimate made with the Lumme and Muinonen function (Eq. (7)) in Figure 2 (dashed line).