Question

During its life, a massive star creates heavier and heavier elements in its core through thermonuclear fusion, leading up to silicon and iron. What is the fate of the iron that is created?

A) The nuclei are split apart by neutron bombardment, creating lighter elements such as carbon, oxygen, and neon.
B) The iron is locked up inside the star forever.
C) The iron is destroyed by later thermonuclear fusion reactions in the core that create even heavier elements such as lead, gold, and uranium.
D) The iron is torn apart by high-energy photons at the end of the star's life.

Answer 1

Iron is the end-product of fusion in a massive star's core, marking the star's eventual collapse because iron fusion absorbs energy, leading to a supernova that ejects the iron into space and forms even heavier elements.

Step-by-step explanation:

During the life of a massive star, a series of nuclear fusion processes create heavier elements in its core, ultimately leading to the production of iron. However, unlike lighter elements, iron does not release energy when it undergoes nuclear fusion. In fact, the fusion of iron is the last step in the sequence of non-explosive element production, and interestingly, fusion of iron atoms absorbs energy rather than releasing it.

Because iron fusion is endothermic, it signifies the end of a star's nuclear 'life'. When there is no longer the release of energy from fusion to counteract gravity, the star begins to collapse under its own weight. This catastrophic collapse heats the core immensely and leads to a supernova explosion, during which the iron in the core, along with other elements, is expelled into space. It is during these violent supernova events that elements even heavier than iron, such as gold and uranium, can be created in a process involving the bombardment of iron nuclei with neutrons (nucleosynthesis).