\begin{table}%t2
\caption {\label{table:comp2}The same as in Table 1 but considering that the radius of the accreted planetesimals is 10~km. }
\begin{tabular}{p{1.1cm} p{1.2cm} p{1.3cm} p{1.2cm} p{1.3cm}}
\hline\hline
Disc density & \multicolumn{2}{p{2cm}}{Previous results} &  
\multicolumn{2}{p{2cm}}{New results}\\
\cline{2-5}
 [MMSN] & Cross- over time [My] & Cross- over mass [${M_{\oplus}}$] & Cross- over 
 time [My] & Cross- over mass [${M_{\oplus}}$]\\
\hline
$\; \; 6$   & $\; \; 4.95$  &  $\; \; 46.70$  & 2.43  & $\; \; 31.80$ \\
$\; \; 7$   & $\; \; 3.53$  & $\; \; 58.70$  & 1.97    & $\; \; 34.80$ \\
$\; \; 8$   & $\; \; 2.65$  & $\; \; 71.40$  & 1.49    & $\; \; 36.80$ \\
$\; \; 9$   & $\; \; 2.00$  & $\; \; 84.85$  & 1.32  & $\; \;38.60$ \\
10  & $\; \; 1.65$  & $\; \;99.00$  & 1.10 & $\; \; 39.90$ \\
\hline 
\end{tabular}
\end{table}