\begin{table}%T2
\caption{ \label{table:times} Comparison of formation times and core 
masses for several disc densities. Planetesimal radius is 100~km.}
%\centering
\small
\begin{tabular}{l p{1.3 cm} p{1 cm} p{1.3 cm} p{1 cm}}
\hline\hline
Disc density  & \multicolumn{2}{c}{Without gas drag} &  \multicolumn{2}{c}
{With gas drag}\\
\cline{2-5}
[MMSN] & Formation time [My] & Core mass [${M_{\oplus}}$] & 
Formation time [My] & Core mass [${M_{\oplus}}$]\\
\hline
%\\
$\; \; 6$   & 17 & 28  & 12  & $\; \; 60$ \\
$\; \; 7$   & 14 & 32  & $\; \; 9$  & $ \; \; 70$ \\
$\; \; 8$   & 11 & 36  & $\; \; 7$  & $\; \;  81$ \\
$\; \; 9$   & 10 & 40  & $\; \; 6$ & $\; \;  91$ \\
10  & $\; \; 8$ & 43  & $\; \; 5$  & 100 \\
\hline 
\end{tabular}
\end{table}