1. Why does a massive star stop fusing?  what is/are the last element(s) fused? 
                and why those?
 
   

   2. a) what type of star becomes a supernova (i.e., what type of star is it JUST BEFORE the supernova explosion)?  How do we know?

b)  What blows off the outer envelope of this pre-supernova star?  as in the case of the planetary nebula, there has to be some physical force (or source of momentum) that pushes the envelope out.... what is it?  (might there be more than one thing?)

   3.  This question is about energy balance.    Clearly some of the energy in supernova
                     event or the post-supernova comes out as light.

                a) what are 5 other IMPORTANT forms or kinds of energy that are present during the
                     supernova explosion or after?

                b) what is the single (input) source of energy that produces all the output energies
                    listed above?    (i.e., in what form is all this energy BEFORE the supernova event?)