Red+Giant.

A red giant is when a sun starts producing fuel like helium or carbon. When it runs out of the fuel it has nothing left. So it will start to cool and contract then the outer shell which is still hot would have a chemical reaction with the core (the part which is cold) then expanding into a __red giant.__ It would expand over up to hundred times and when it does it will swallow up most of the planets then it will explode. That will not happen in another four billion years with our sun.