A slightly schematized/simplified version of one form of the ancient symbol of the Mesopotamian sun-god Shamash, with alternate pointy and wavy rays.  According to Gods, Demons, and Symbols of Ancient Mesopotamia: An Illustrated Dictionary by Jeremy Black and Anthony Green (1992, ISBN 0-292-70794-0), p. 168, it occurs "from the Akkadian down to the Neo-Babylonian period", and "The Akkadian names of the symbol were šamšatu and niphu.  It was often represented on a pole as a standard."

For modern symbols which incorporate a version of the Shamash sun-symbol, see File:Flag of the Assyrian people.svg, File:Iraq state emblem CoA 1959-1965 Qassem.svg etc.
This is an SVG version of File:Star of Shamash.png (attempting to duplicate the appearance of the PNG file, but generated from abstract geometry and symmetrical), converted from the following vector PostScript source code:

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18.5 0 35 -9 45 -13.5 rcurveto 10 -4.5 26.5 -13.5 45 -13.5 rcurveto}for
stroke}def 287 287 translate 1 -1 scale 5.2 setlinewidth 0 0 280.5 0 360 arc
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eq{1 -1 scale}if 178 -13.5 25 sub moveto A 178 -13.5 52 add moveto A grestore
90 rotate}for grestore 18 setlinewidth 4{42.426 42.426 moveto 238 0 lineto
42.426 -42.426 lineto stroke 90 rotate}repeat showpage
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AnonMoos