"After" and "Before" real images of a supernova by NASA |
For a better understanding, please go through this post - How stars work ?
This event occur at the end of a star's ( particularly big sized stars = minimum mass 8 times that of the sun ) lifetime, when its nuclear fuel runs out, the star unable to provide necessary resisting force towards the gravity, gravity crushes the star and it's core to itself. Gravity does this so strongly that even the atoms crush together, making the core more and more unstable and intense so at certain point the energy building up overcomes gravity and causes a blast of shock-wave that ejects the star's envelope into interstellar space.
This event occur at the end of a star's ( particularly big sized stars = minimum mass 8 times that of the sun ) lifetime, when its nuclear fuel runs out, the star unable to provide necessary resisting force towards the gravity, gravity crushes the star and it's core to itself. Gravity does this so strongly that even the atoms crush together, making the core more and more unstable and intense so at certain point the energy building up overcomes gravity and causes a blast of shock-wave that ejects the star's envelope into interstellar space.