A question about supernova. I assumed when a star became a supernova it exploded and it threw out all its matter for miles. Then I read the star doesn't explode it collapses into a denser body all that is ejected is a shockwave and heat and light. Which is correct?Also because I am assuming that stars collapse into a denser body, how does the theory that there were no heavy elements until the first generation of stars exploded sending heavy elements across the universe work?To escape a planets gravitational pull requires the projectile to be moving at X m/s if the star collapses into a denser body the gravitational pull will increase requiring an even faster speed for any projectile. If the star collapses and becomes a dark hole not even light can escape this gravitational pull. Just wondering how heavy elements are supposed to have spread throughout the universe taking all this into account