Better idiomatic way to print a centered "starlet" (asterisk)?

Question

I need to print what the publisher calls "a starlet" (asterisk).

I devised the code below, but I am not sure if it is a sound code, i.e., it won't cause problems later on, within other commands and the text stream.

Is that the idiomatic way to print a special character (in this case, mathabx's \varstar), centered and with 1 blank line above and below?

I am using \vgrid in order to check the vertical alignment is preserved as precisely as possible, in respect to the underlying grid.

\documentclass[
DIV=calc,
twoside,
openright,
twocolumn=false,
titlepage,
numbers=noenddot,
headinclude=true,
footinclude=true,
]{scrbook}

\usepackage{kantlipsum}
\usepackage{mathabx}
\newcommand{\aster}{$\varstar$} 

\usepackage{vgrid}

\makeatletter
\newcommand{\starlet}{% 
  \par
  \vskip -0.5pt
  \noindent
  \parbox{\linewidth}{
    \begin{center}
      \aster
    \end{center}
  }
  \par
  \vskip 0.6pt % make it fit the grid
  \noindent
}
\makeatother

\begin{document}
\kant[1]
\starlet
\kant[1]
\end{document}

Answer 1

I suggest using \centering instead of {center} since the former adds no vertical space and let’s you control the spacing exactly it without the need of fiddling with corrections. To use \centering only for a part of your document enclose it in a group, i.e. {…}, and add a \par after it but inside the group. Then use \(add)vspace with \baselineskip as value to add blank lines before and after.

\usepackage{adjustbox,noindentafter}

\newcommand{\starlet}{%
  {% 
    \par
    \addvspace{\baselineskip}%
    \centering
    \adjustbox{raise=1pt}{\aster}%
    \par
    \vspace{\baselineskip}%
  }%
  \NoIndentAfterThis
}

Some notes

• \addvspace chacks wether there is already some space before and adds it only when necessary. At the of the definition you can use the normal \vspace since there won't be any space before it.
• \NoIndentAfterThis (needs noindentafter) is the way to prevent the indent after the command. This must be outside of the group. (see Reliable code for automatic \noindent after specific environments?)
• If you want to center \aster in the line, one way is to use \adjustbox{raise=1pt}{\aster} (needs adjustbox) or another way is \raisbox{1pt}{\aster} (needs graphicx).
• The \makeatletter/other pair isn’t needed here since you don’t use commands containing @ as part of their name.

---

To center a single line (box) one can also use \hspace with \fill as a value:

\newcommand{\starletII}{%
  \par
  \addvspace{\baselineskip}%
  \hspace*{\fill}% without the star space would be ignored it it
         % begins/ends a line
  \adjustbox{raise=1pt}{$\star$}%
  \hspace*{\fill}
  \par
  \vspace{\baselineskip}%
  \NoIndentAfterThis
}

Answer 2

(Answer updated to incorporate the fact that use of \varstar, rather than of some arbitrary asterisk symbol, is required.)

I suppose an idiomatic LaTeXy way of creating a blank line of height \baselineskip is to type \par\null\par. To center-set a given symbol, one could use the TeX "primitive" command \centerline. In the code below, the command \starlet sandwiches the instruction \centerline{$\varstar$} between two sets of \par\null\par instructions. The total height of the output generated by \starlet is exactly 3\baselineskip, automatically preserving any grid alignment that may be in place.

\documentclass[twocolumn]{article}
\usepackage{mathabx}  % for \varstar symbol

\newcommand\starlet{%
  \par\null\par%  a blank line of height \baselineskip
  \centerline{$\varstar$}%  center-set the ask
  \par\null\par}% another blank line of height \baselineskip

%% Just for this example:
  \setlength\parindent{0pt} 
  \usepackage[textwidth=2.95in,showframe]{geometry}

\begin{document}
Some meaningless fluff.

Some meaningless fluff.

Some meaningless fluff.

Some meaningless fluff.

Some meaningless fluff.

\newpage  % induce a column break
Some meaningless fluff.

\starlet

Some meaningless fluff.
\end{document}