TERRAPUB Earth, Planets and Space

Earth Planets Space, Vol. 50 (Nos. 6, 7), pp. 477-480, 1998

The isophote maps of the Gegenschein obtained by CCD observations

Masateru Ishiguro1, Hideo Fukushima2, Daisuke Kinoshita3, Tadashi Mukai1, Ryosuke Nakamura4, Jun-ichi Watanabe2, Takeshi Watanabe1, and John F. James5

1The Graduate School of Science and Technology, Kobe University, Kobe 657-8501, Japan
2National Astronomical Observatory, Mitaka, Tokyo 181-8588, Japan
3Department of Physics, Faculty of Science, Tohoku University, Sendai 980-77, Japan
4Information Processing Center, Kobe University, Nada, Kobe 657-8501, Japan
529, Merchants' Quay, Salford, M5 2XF, England

(Received December 8, 1997; Revised January 16, 1998; Accepted February 3, 1998)

Abstract: We summarize the results of our Gegenschein observations at Norikura (altitude 2876m, Japan) in Sept. 18, 1996, and at Kiso (altitude 1130m, Japan) in Feb. 9-14, and March 4 and 5,1997. The instrument consisting of fish-eye lens or the wide angle lens attached to the cooled CCD camera was used with green filter. It is found that the position of the maximum brightness near the antisolar point (the Gegenschein) is slightly deviated approximately 0. °4 from the antisolar point to the south in September, whereas nearly 0. °7 to the north in February/March. Furthermore, a gradient of the relative intensity along a line perpendicular to the ecliptic is remarkably different with changing seasons, i.e. the brightness decreases faster towards the north in September, in contrast with its quick decrease towards the south in February/March. Our observed evidence suggests that these variations of the peak position and the brightness gradient of the Gegenschein are caused by the annual motion of the Earth with respect to the plane of the zodiacal cloud, and does not conflict with the predictions deduced from the cloud model having its symmetric plane beyond the Earth's orbit coinciding with the invariable plane of the solar system.

Corresponding author E-mail: ishiguro@komadori.planet.kobe-u.ac.jp

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