`\bigstar` produces a black star.
What is the LaTeX command for white or unfilled `\bigstar`?

The `unicode-math` package has a command `\bigwhitestar`, but I am not able to use it in the usual way. When I compile with `\usepackage{unicode-math}`, I get the following error:

```
! Package unicode-math Error: Cannot be run with pdfLaTex!
(unicode-math)         Use XeLaTeX or LuaLaTex instead.

```

PS: I need the big white star symbol to reference a point in a Matlab generated figure.
I cannot compile with xetex or xelatex because they do not use the conference style file properly, i.e. the output looks quite different from that of latex.