Spikes around circle using tikzpicture

You can use polar coordinates to draw the lines.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{positioning,calc,arrows.meta}
\begin{document}
\begin{center}
  \begin{tikzpicture}
    \coordinate[label= below left:$$] (origo) at (0,0);
    \coordinate[label = below left:$$] (origos) at (7,0);
    \draw[line width = 1pt, -{Stealth[length=3mm]}] (origo) -- (3.3,0) node[below]{$x$};
    \draw[line width = 1pt, -{Stealth[length=3mm]}] (origo) -- (0,3.3) node[left]{$y$};
    \draw[line width= 1pt, -{Stealth[length=3mm]}] (origo) -- (-2,-1.7) node[below]{$z$};
    \node[] at (0.5,3.3) {\textsf{S}};
    \begin{scope}[xshift = 7cm]
      \draw[line width = 1pt, -{Stealth[length=3mm]}] (0,0) -- (3.3,0) node[below]{$x'$};
      \draw[line width = 1pt, -{Stealth[length=3mm]}] (0,0) -- (0,3.3) node[left]{$y'$};
      \draw[line width= 1pt, -{Stealth[length=3mm]}] (0,0) -- (-2,-1.7) node[below]{$z'$};
      \node[] at (0.5,3.3) {\textsf{S}$^{\prime}$};
    \end{scope}
    \draw[-{Stealth[length=3mm]}, line width=0.8pt](5.5,2.2) -- (8.5,2.2) node[right]{$v$};
    \fill[black] (11,2.2) circle (4pt);
    \foreach \ang in {22.5,45,...,360}{%%%%%%%%%%%%%% Added
      \draw[ultra thick] (11,2.2) +(\ang:6pt) -- +(\ang:11pt);
    }
    \node[] at (11,3) {\small \textsf{Begivenhed}};
    \node[] at (12.3,2.4) {\small $(t, \, x, \, y, \, z)$};
    \node[] at (12.5,1.8) {\small $(t', \, x', \, y', \, z')$};
    \draw[|-{Stealth[length=3mm]}, line width=0.8pt] (0.2,1.4) -- (6.8,1.4) node[above] at (3.5,1.4) {$vt$};
    \draw[|-{Stealth[length=3mm]}, line width=0.8pt] (7.2,1.4) -- (11,1.4) node[above] at (9.1,1.4) {$x^{\prime}$};
    \draw[|-{Stealth[length=3mm]},line width=0.8pt] (0.2,0.8) -- (11,0.8) node[above] at (5.6,0.76) {$x$};
  \end{tikzpicture}
\end{center}
\end{document}

In the original code, you can see that the symbol is generated by \ding{90}.

As the preamble is missing in both your code examples, one has to guess, but it turns out the command comes from the pifont package:

\documentclass{article}

\usepackage{tikz}
\usetikzlibrary{arrows.meta}

\usepackage{pifont}

\begin{document}

\begin{center}

\begin{tikzpicture}

\coordinate[label= below left:$$] (origo) at (0,0);

\coordinate[label = below left:$$] (origos) at (7,0);

\draw[line width = 1pt, -{Stealth[length=3mm]}] (origo) -- (3.3,0) node[below]{$x$};

\draw[line width = 1pt, -{Stealth[length=3mm]}] (origo) -- (0,3.3) node[left]{$y$};

\draw[line width= 1pt, -{Stealth[length=3mm]}] (origo) -- (-2,-1.7) node[below]{$z$};

\node[] at (0.5,3.3) {\textsf{S}};

\begin{scope}[xshift = 7cm]

\draw[line width = 1pt, -{Stealth[length=3mm]}] (0,0) -- (3.3,0) node[below]{$x'$};

\draw[line width = 1pt, -{Stealth[length=3mm]}] (0,0) -- (0,3.3) node[left]{$y'$};

\draw[line width= 1pt, -{Stealth[length=3mm]}] (0,0) -- (-2,-1.7) node[below]{$z'$};

\node[] at (0.5,3.3) {\textsf{S}$^{\prime}$};

\end{scope}

\draw[-{Stealth[length=3mm]}, line width=0.8pt](5.5,2.2) -- (8.5,2.2) node[right]{$v$};

%\fill[black] (11,2.2) circle (4pt);

\node[scale=3] at (11,2.2) {\ding{90}};

\node[] at (11,3) {\small \textsf{Begivenhed}};

\node[] at (12.3,2.4) {\small $(t, \, x, \, y, \, z)$};

\node[] at (12.5,1.8) {\small $(t', \, x', \, y', \, z')$};

\draw[|-{Stealth[length=3mm]}, line width=0.8pt] (0.2,1.4) -- (6.8,1.4) node[above] at (3.5,1.4) {$vt$};

\draw[|-{Stealth[length=3mm]}, line width=0.8pt] (7.2,1.4) -- (11,1.4) node[above] at (9.1,1.4) {$x^{\prime}$};

\draw[|-{Stealth[length=3mm]},line width=0.8pt] (0.2,0.8) -- (11,0.8) node[above] at (5.6,0.76) {$x$};

\end{tikzpicture}

\end{center}


\end{document}

This is one of the cases where the decoration with ticks doesn't work because the dimensions get too small.

\documentclass[tikz,border=3.14mm]{standalone}
\usetikzlibrary{arrows.meta}
\begin{document}
\begin{tikzpicture}

\coordinate[label= below left:${}$] (origo) at (0,0);

\coordinate[label = below left:${}$] (origos) at (7,0);

\draw[line width = 1pt, -{Stealth[length=3mm]}] (origo) -- (3.3,0) node[below]{$x$};

\draw[line width = 1pt, -{Stealth[length=3mm]}] (origo) -- (0,3.3) node[left]{$y$};

\draw[line width= 1pt, -{Stealth[length=3mm]}] (origo) -- (-2,-1.7) node[below]{$z$};

\node[] at (0.5,3.3) {\textsf{S}};

\begin{scope}[xshift = 7cm]

\draw[line width = 1pt, -{Stealth[length=3mm]}] (0,0) -- (3.3,0) node[below]{$x'$};

\draw[line width = 1pt, -{Stealth[length=3mm]}] (0,0) -- (0,3.3) node[left]{$y'$};

\draw[line width= 1pt, -{Stealth[length=3mm]}] (0,0) -- (-2,-1.7) node[below]{$z'$};

\node[] at (0.5,3.3) {\textsf{S}$^{\prime}$};


\end{scope}

\draw[-{Stealth[length=3mm]}, line width=0.8pt](5.5,2.2) -- (8.5,2.2) node[right]{$v$};

\foreach \X in {0,30,...,330}
{\draw (11,2.2) -- ++ (\X:11pt);}
\fill[white] (11,2.2) circle (6pt);
\fill[black] (11,2.2) circle (4pt);


\node[] at (11,3) {\small \textsf{Begivenhed}};

\node[] at (12.3,2.4) {\small $(t, \, x, \, y, \, z)$};

\node[] at (12.5,1.8) {\small $(t', \, x', \, y', \, z')$};

\draw[|-{Stealth[length=3mm]}, line width=0.8pt] (0.2,1.4) -- (6.8,1.4) node[above] at (3.5,1.4) {$vt$};

\draw[|-{Stealth[length=3mm]}, line width=0.8pt] (7.2,1.4) -- (11,1.4) node[above] at (9.1,1.4) {$x^{\prime}$};

\draw[|-{Stealth[length=3mm]},line width=0.8pt] (0.2,0.8) -- (11,0.8) node[above] at (5.6,0.76) {$x$};

\end{tikzpicture}

\end{document}