The style file astron.bst causes BibTeX to produce a document.bbl file with a list of references according to the usual format:
The label is, of course, the label which you use in the\begin{thebibliography}{}
\bibitem[
key]{
label}
bibliography entry
\end{thebibliography}
\cite{
label}
and \cite*{
label}
calls in your LaTeX document, and by which BibTeX recognizes entries
in the database.bib file.
The style file astron.bst causes BibTeX to produce keys
with the format: {
Author}{
year}
.
The style file astron.sty causes LaTeX to replace a
\cite{
label}
call by the text `(Author, year)',
and a \cite*{
label}
call by the text `(year)'.
Due to the definition of \@biblabel
in astron.sty, the key
is not printed in the actual list of references.