The majority of massive stars, at the point in time when they explode as supernovae, have become

The life cycle of a star ends when it undergoes a huge explosion called a supernova. It happens because the center, or core, of the star collapses in less than a second. The blown parts during the explosion leaves a contracting core after the explosion. I hope my answer has come to your help. God bless and have a nice day ahead!