Resolving color differences of comet 41P/Tuttle-Giacobini-Kresák

Abstract

Three different measurement campaigns have resulted in three drastically different sets of color measurements of Comet 41P/Tuttle-Giacobini-Kresák, ranging from a strongly red to a strongly blue color. Although the color slope is normalized to the wavelength range between the filters used, this only serves to partially normalize the resulting color, as the reflectance of cometary dust has a very strong dependence on particle absorption, which may change significantly over the wavelength range of measurement. We demonstrate that the different measurements are physical and are consistent with real materials; for example, we are able to reproduce the color measured during one epoch in which both strong blue and red color slopes were measured almost simultaneously in different filter sets with the mineral dust pyroxene. Such measurements with different filter sets serve as an additional constraint in modeling dust properties.