\documentclass[a4paper]{article}

\usepackage{graphicx,times}
\usepackage{subfigure}         
\usepackage{natbib}
\usepackage{amssymb,amsmath}

\usepackage{geometry}
\geometry{left=2cm,right=2cm,top=2cm,bottom=2cm}

\begin{document}
 
\begin{figure*}
  \centering
  \subfigure[Radial Velocity Method]{\includegraphics[width=2in]{s1.eps}}
  \subfigure[Moons of Jupiter]{\includegraphics[width=2in]{s2.eps}}
  \caption{ Demo }
  %\label{fig1}
\end{figure*}

\end{document}

排版效果如圖：