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   71070
   We discovered the "X-ray reflection nebular" Sgr B2 which emits only
   indirect X-rays by irradiated external source. This object gave us very
   rich information about the environment of our Galactic center. It gave
   a limit on the abundance of heavy elements and the mass of the giant
   molecular cloud. Moreover, it indicates the past activity of the
   Galactic center from the study of incident X-rays. We propose the
   observation of Clump 2 cloud, which is the second candidate of this "X-
   ray reflection nebular" becouse it also radiates strong 6.4-keV line
   emission. This cloud will provide more information for us. We can
   establish this new classification "X-ray reflection nebular" and decide
   the position of the primary X-ray source from the comparison of two
   cloud.
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