Neil DeGrasse Tyson on Ristar: "A star is merely a spheroid mass of plasma and burning gases held together by its own gravity. First of all, by its very definition a star's position is fixed in the universe and therefore it would be impossible for one to "travel" anywhere, let alone via spectacular gymnastic skills. And second, they burn at astronomical levels, billions of BTUs of heat and massive radiation. Were a star to come to your planet to save it from an alien invasion, never mind if that planet is underwater, fire, or ice-themed, it would reduce that planet into just-barely molecular dust before even getting a chance to pole-vault into a baddie of the moment."