The Starspots are tiny Interference Black Holes and the Origin of Variable Stars.

We have discovered that starspots are not only cool but also tiny black holes able to grow and make Herbig Haro systems. ( Q-FFF Theory)
This means that we may assume that rotating stars ( which all of them seem to do) become variable stars at the moment they are equipped with large enough starspots.

At the same time, these internal starspots are tiny but growing black holes (Former Crashed Comets) are supposed to be accelerating the so called Super Nova explosion process.  

This means that not very much of the Oxygen content could be consumed by the star.  This is even observed  in recent S Nova Nebula.

An other interesting image suggests also that Starspots are the same as tiny Black Holes.