Why does a star die once it has iron?

Question

I found out that iron is the death element for stars, but I couldn't find why can anyone knowledgeable on stars explain why iron causes the star to die?

Answer 1

This is the binding energy of some elements as a function of their number of nucleons

Since fusion leads to a higher number of nucleons, what a star does is to progressively move from left to right on this plot.

So if you start on the left, say H, you merge two, and the result has a larger binding energy, so energy is released. But that behavior is broken when you reach Fe$^{56}$, at that point, you need extra energy. Since the star cannot produce it, it stops fusing material, and it dies off

Answer 2

A star "dies" when the fusion stops. 56Fe is the most stable nucleus that exists so it is the ultimate fusion product. Any nucleons contained in it no longer contribute to the energy production.