Substances of cometary grains estimated from evaporation and radiation pressure mechanisms |
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| Authors: | Keiji Saito Shuzo Isobe Kimihiko Nishioka Tatsuro Ishii |
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| Institution: | Tokyo Astronomical Observatory, University of Tokyo, 2-21-1, Osawa, Mitaka, Tokyo 181, Japan;Olympus Optical Company Ltd., 1-43-2, Hatagaya, Shibuya, Tokyo 151, Japan;1964, Akanuma, Hatoyama-mura, Saitama 350-03, Japan |
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| Abstract: | The shape and intensity distribution of tails for several large comets are estimated on the basis of grain properties in the solar radiation field. The following results are obtained: (1) The ratio of the maximum radiation pressure force to the gravitaional force acting on dust grains in cometary tails is found to be less than 2.5. This means that grains such as graphite particles in the size range 0.02–0.2 μm do not exist in them, because such particles would allow forces greater than 2.5 (2) Tail substances supplied near the time of perihelion passage for the Sun-grazing comet Ikeya-Seki (1965 VIII) and Comet Seki-Lines (1962 III) were composed of particular grains which had values of radiation pressure ratio less than 1.0. Therefore, it is concluded that the material was composed of silicate grains only, since iron grains had sublimated and there were no graphite particles. |
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