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   PR # 21158
    We propose the observation of cluster pair of A401 &A399.The clusters
    are similar to each other; cD clusters, high temperatures, large lumi
    nosities. Probably, they were born at the same time and have traced a
    similar evolutional track. Since the relative velocity is small (800 
    km/s) and the separation  between them is only 6Mpc, they are bound  
    gravitationally. They will merge and become one cluster. Einstein obs
    ervation give us a hint of X-ray emission from the region between the
    two clusters. The most important parameters to decide the dynamical  
    evolution are the depth and the form of the gravitational potential  
    of the whole system. We propose mapping observation of the system and
    determin temperature, surface brightness and gravitational potential 
   and disscuss merging of cluste
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