A high-mass star evolves towards core collapse. Which is NOT true about the natu

Question

A high-mass star evolves towards core collapse. Which is NOT true about the nature of the fusion occurring in the core from one stage of evolution to the next?  

The mass of each stage’s inputs elements is less in each successive stage.  

Less energy is extracted in each successive stage.  

Fusion occurs at higher temperature in each successive stage.  

There are fewer atoms available for fusion in each successive stage.

Fusion occurs faster in each successive stage.  

The mass of each stage’s inputs elements is less in each successive stage.  

Less energy is extracted in each successive stage.  

Fusion occurs at higher temperature in each successive stage.  

There are fewer atoms available for fusion in each successive stage.

Fusion occurs faster in each successive stage.  

Explanation / Answer

The mass of each stage’s inputs elements is less in each successive stage.

The process is the following

Each additional step produces progressively heavier nuclei (implying more mass), which release progressively less energy when fusing. In addition, from carbon-burning onwards, energy loss via neutrinoproduction becomes significant, leading to a higher rate of reaction than would otherwise take place. This core is under huge gravitational pressure. As there is no fusion to further raise the star's temperature to support it against collapse. The rapidly shrinking core heats up, producing high-energy gamma rays that decompose iron nuclei into helium nuclei and free neutrons via photodisintegration. As the core's density increases, it becomes energetically favorable for electrons and protons to merge, producing neutrons and neutrinos.

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