\begin{table}
%\begin{center}
\par
\caption{{Results of the collision between $\nu$~ring particles
and the close satellites (Rosalind and Portia) after
$1000$~years.}}
\label{T-nu}
\begin{tabular}{lcccccc} \hline\hline
Particle size & \multicolumn{3}{c}{Rosalind} & \multicolumn{3}{c}{Portia}\\\\[-3mm]
\cline{2-4}\cline{5-7}\\[-3mm] ($\mu$m) & $N_\%$ & $\overline{T}$ (years)
& $\overline{v}$ (m~s$^{-1}$)& $N_\%$ & $\overline{T}$
 (years)
& $\overline{v}$ (m~s$^{-1}$) \\ 
\hline
1 & 42 & 31 & 164 & 52 & 12 & 163 \\
3 & 23 & 131 & 73 & 31 & 120 & 88 \\
5 & 19 & 147 & 69 & 29 & 176 & 80 \\
10 & 16 & 196 & 58 & 27 & 234 & 79 \\ \hline
\end{tabular}
%\end{center}
\par
\end{table}