Combining Asterisk Above

It adds an asterisk-shaped accent above the preceding character.

A 2007 IEEE request for the STIX set of mathematical fonts proposed it as an accent for TeX, LaTeX, and MathML. That explains its math accent use: it can sit over a variable or another symbol without taking a text position of its own.

A 2010 proposal documents it in notation for chanting the Sama Veda. There it is a secondary svara (pitch mark), qualifying a primary mark as a special recitation pattern. A related proposal considered reusing the math mark, then recommended a distinct Vedic character because that sign has its own meaning in Vedic notation.

Why does the mark move or show a circle?

It needs a base and a font that can position it.

Place it after the symbol it modifies. As a nonspacing mark, it joins the base's grapheme cluster—the unit many editors move through as one character. Other combining marks can stack farther from the base.

Without a usable base, or when a font cannot position the mark over that base, a renderer may show a dotted-circle fallback or place it awkwardly. That changes the display, not the text sequence.