||What's the biggest star? It is difficult to determine
the size of a star. If you mean the star with the biggest radius then it could
be a star like Beutelguese in Orion which is a red giant that is nearing
the end of its life. If you meant the amount of mass that the star has ,
it could be a black hole that is very massive, but not big in size. To
determine the radius of a star we need to measure the brightness, the
distance to the star, and the color. It is hard to know all of these. The
color of the star is a measure of its part in the life cycle of stars.