The death of massive stars
Although type 1A supernova explosion is an immense one, there is a type 2 supernova that signals the death of much more massive stars (about 8-10 times greater than the mass of the Sun)
When massive stars run out of nuclear fuel, the core starts to shrink. As the core shrinks, the outer layers swell into a Red Super Giant. Inside its core, new nuclear fusion begins causing the star to expand again. Finally, when the fuel of the nuclear fusion runs out the core is made purely of iron. Consequently, the iron core collapses in an extremely huge supernova explosion, where 1st generation stars died
Cassiopeia A supernova remnant
the Bug Nebula
G292.0+1.8:
Crab supernova remnant