No one knows the absolute answer to this very interesting question, but many would love to know what the answer is!

We can at the least say the number is so huge that we cannot comprehend it; given that there are billions of stars in each galaxy and there may be for all we know trillions of galaxies then the number is truly collosal.

It is also of course in a constant state of flux as stars are born and other stars die or collide and change state - therefore the number is also ever changing.