\begin{table}%t1
  \caption{Typical timescales for the different of structures on the 
    solar surface. \label{tab:comps}}
%\centering
\par
         \begin{tabular}{p{0.5\linewidth}l}
            \hline
            \hline
            Component & Timescale~$B$~(s) \\
            \hline
            Active~regions     & 1~to~$3 \times 10^7$ \\
            Super-granulation  & 3~to~$7 \times 10^4$ \\
            Meso-granulation   & $\simeq$8000 \\
            Granulation        & 200~to~500 \\
            Bright~points      & $\simeq$70 \\
            \hline
         \end{tabular}
\end{table}