Regular Expression - Not string literal

Regular Expression - Not string literal

With the regular expression \*\*([^\*]*)\*\* I can match multiple groups
of text inside **'s such as:
this **is** a **test**
Returning is & test.
Given the string that's **right * a test**, how do I adjust my expression
to return right * a test? How do I get my expression to exclude two *'s
instead of just one?
http://regex101.com/r/aD3pC2