\begin{table}%t4
\caption{\label{t:ceres} Physical and orbital parameters of Ceres (\protect\url{http://ssd.jpl.nasa.gov/}).}
%\centering
\par
\begin{tabular}{ll}
\hline\hline\noalign{\smallskip}
mass & $9.4\times10^{20}$~kg \phantom{$\displaystyle K^{2^3}$} \\
equatorial radius & 487.3~km \\
polar radius & 454.7~km \\
rotational period & 0.3781~days \\
orbital period & 1680.5~days \\
semimajor axis & 413~832.587~km \\
heliocentric gravitational constant & $1.327\times10^{11}~{\rm km^3/s^2}$ \\ 
\hline
\end{tabular} 
\end{table}