Fading of Sunlight Scattered by a Meteoric Cloud of the Leonid Parent Comet 55P/Tempel-Tuttle

During the Leonid meteor shower in 1998, a faint glow in the direction of the dust trail of comet 55P/Tempel-Tuttle was discovered using photometric observations (Nakamura et al. 2000, ApJ, 540, 1172). It is considered that this glow was due to sunlight scattered by sub-millimeter-sized dust particles located along the orbit of 55P/Tempel-Tuttle. To examine the spatial distribution of the dust particles, we observed the sky in the direction of the dust trail on 2001 November 18, but the data taken at this epoch showed no significant evidence of scattered sunlight. Based on data obtained at both epochs of observation, 1998 and 2001, we discuss two possible scenarios for the fading of the meteoric cloud: sublimation of volatiles in the dust grains, and/or an expansion of the width of the trail. If the latter scenario is correct, the trail at the time of the 2001 observations would have been four-times wider than in 1998.