Do not touch your starfish w/your bare hands but rather with some gloves (latex)or a spatula or something and see if it's mouth..the disc underneath.. looks ok,also check that your star is still stiff NOT soft/mushy..if it is soft/mushy that is a good sign it has died and it could be lethal to the rest of your tank so it must be removed quickly and carefully..
Hope the best for you..
Katara