\begin{table}%t3
      %\centering
\par
      \caption{Our results for the spin-orbit motion of Mercury. The 
      spin-orbit period verifies the relation: $\widetilde{P} = 2 P_{\lambda}=3 P_{\varphi}$.\label{periode}}
    $$  \begin{tabular}{lcr}
             \hline  
             \hline	
     \multicolumn{3}{c}{Mercury}\\
       \multicolumn{3}{c}{Spin-orbit characteristic period}\\
       \hline
        $\Phi$ (1st proper frequency) & = & 15.847 yrs \\
        $\Psi$ (2nd proper frequency) & = & 1066 yrs \\
        $\Pi$ (orbital precession) & = & 278 898 yrs \\
        $P_{\lambda}$ (orbital period) &  = & 87.969 days \\
        $P_{\varphi}$ (rotational period) & =  & 58.646 days \\
        $\widetilde{P}$ (spin-orbit period) & = & 175.95 days \\
       \hline        
        \end{tabular}$$
    \end{table}