\documentclass{aa}  

\usepackage{graphicx}
\usepackage{txfonts}
\usepackage[options]{hyperref}

\begin{document} 

   \title{Make a suitable title: my paper on the cosmic microwave background and formation of structures in our Universe}

   \author{H. A. Winther\inst{1}}

   \institute{Institute of Theoretical Astrophysics,  
                University of Oslo,  0315 Oslo,  Norway\\
              \email{h.a.winther@astro.uio.no}
             }

   \date{}

  \abstract{An abstract for the paper. Describe the paper. What is the paper about, what are the main results, etc.}

   \keywords{   cosmic microwave background  --
                large-scale structure of Universe
               }

   \maketitle

\section{Introduction}
Write an introduction here. Give context to the paper. Citations to relevant papers. You only need to do this in the end for the last milestone.

\section{Milestone I}
Some introduction about what it is all about.

\subsection{Theory}
The theory behind this milestone.

\subsection{Implementation details}
Something about the numerical work.

\subsection{Results}
Show and discuss the results.

\section{Milestone II}
Some introduction about what it is all about.

\subsection{Theory}
The theory behind this milestone.

\subsection{Implementation details}
Something about the numerical work.

\subsection{Results}
Show and discuss the results.

\section{Milestone III}
Some introduction about what it is all about.

\subsection{Theory}
The theory behind this milestone.

\subsection{Implementation details}
Something about the numerical work.

\subsection{Results}
Show and discuss the results.

\section{Milestone IV}
Some introduction about what it is all about.

\subsection{Theory}
The theory behind this milestone.

\subsection{Implementation details}
Something about the numerical work.

\subsection{Results}
Show and discuss the results.

\section{Conclusions}

Write a short summary and conclusion in the end. 

\begin{acknowledgements}
      I thank my mom for financial support!
\end{acknowledgements}

\begin{thebibliography}{}

  \bibitem[Baker(1966)]{baker} Baker, N. 1966,
      in Stellar Evolution,
      ed.\ R. F. Stein,\& A. G. W. Cameron
      (Plenum, New York) 333
\end{thebibliography}

\end{document}