Question: what causes a supernova?

Linda Cremonesi answered on 18 Jun 2014:

Supernova explosions come at the end of a star’s life!
Stars can die in 2 ways. Small stars (like the sun) are called white dwarf and they will not die forming a black hole, but would simply slowly “turn off”.

Bigger stars behave differently. So there are 2 opposite forces inside stars:
– on one side we have forces trying to make the star expand (making it bigger and bigger) through nuclear reactions inside their core (these nuclear reactions are responsible for the light you see from the stars! That’s why they’re so bright!).
– on the other side the gravitational force (which is the same force that keep you attached to this planet) will try to make the star “shrink”.

These 2 forces battle continuously to stay in an equilibrium state, but after a long time the fuel for nuclear reactions runs out so we get a big explosion (a supernova explosion with lots of neutrinos generated) and the star will shrink into itself to become a very small point of infinite mass and density! And that’s a black hole!