Earth Planets Space, Vol. 62 (No. 1), pp. 13-16, 2010
T. Kadono1, S. Sugita2, T. Ootsubo3, S. Sako4, T. Miyata4, R. Furusho5, M. Honda6, H. Kawakita7, and J. Watanabe5
1Institute of Laser Engineering, Osaka University, Japan
2Department of Complexity Science and Engineering, the University of Tokyo, Japan
3Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Japan
4Institute of Astronomy, the University of Tokyo, Japan
5National Astronomical Observatory of Japan, Japan
6Kanagawa University, Japan
7Department of Physics, Kyoto Sangyo University, Japan
(Received July 31, 2008; Revised December 3, 2008; Accepted December 10, 2008; Online published February 12, 2010)
Several observations of dust grains ejected from the comet 9P/Tempel 1 by the Deep Impact event strongly suggest that the evaporation and expansion of volatiles occurred and that the vapor accelerated some dust grains. When grains are accelerated by gas, size sorting should occur, that is, larger grains tend to stay closer to the nucleus, while smaller grains is pushed farther away. This means that the light at each distance is emitted from identical-sized grains. Hence, we can estimate the size distribution of grains based on the flux as a function of the distance from the nucleus. A simple evaluation indicates that the size distribution of grains with a size larger than ∼10 μm is expressed as a power law and the index is ∼-4. This is expected to be an alternative method to estimate the size distribution of grains, though detailed analyses and numerical simulations should be necessary to evaluate the error of this method.
Key words: Jupiter family comets, Deep Impact, ejecta, size distribution, MIR observation, SUBARU telescope.