For most stars, including our Sun:
* The heaviest element is usually Iron (Fe). Iron is the most stable element in terms of nuclear fusion. When a star's core runs out of hydrogen and helium to fuse, it starts fusing heavier elements, culminating in iron. Iron fusion does not release energy, it actually consumes it. This leads to the star's collapse and the eventual supernova explosion.
For very massive stars:
* Heavier elements like Nickel (Ni) can also be found in the core. These elements are produced in the final moments before the star's core collapses.
For very rare and extremely massive stars:
* Elements even heavier than iron, like Uranium (U), can be produced in the core. These elements are only created in extremely energetic events like supernovae.
It's important to note that the elements present in a star's core are constantly changing as the star evolves. The core's composition shifts as different nuclear fusion reactions take place. The heaviest element present at the time of the star's death is the most notable, but it's only one snapshot in the star's life story.
