Will Our Sun Expand and Go Nova or Shrink into a Black Hole?

[Mr Greene]

What conditions cause a star to do one or the other?

Mass, in essence if a star has sufficient mass it will eventually undergo a core collapse resulting a singularity and creating a black hole. We have observed Magnetars 40X the mass of the Sun, therefore in order to produce a black hole a star must be larger than 40X the mass of the Sun.

As a star like the Sun uses it's fuel of Hydrogen it will eventually run out and start fusing heavier elements in sequence;
Helium, Lithium, Beryllium etc. during which it loses control of it's outer layers which expand becoming a Red Giant enveloping the inner planets. When it reaches the point that it has to fuse Iron the reaction absorbs energy instead of releasing it, the outer layers cool and collapse into the core, this triggers an Implosion better known as a Super Nova destroying the star and any planets orbiting and with a star the size of the Sun leaving a White Dwarf with an expanding planetary nebula.