This card happens to be one of the "evil" Pokemon from the Neo Set. The backgrounds on these cards is black. They had to print a white star on them so that it would not be lost in the black background. The White Star on this card, unlike it's HCTR, Imakuni's Doduo, and ___ Chansey White Symbol Counterparts, does not mean any additional rarity to the card. Good question, though.
Scott