A High-Mass Star near the End of Its Life Undergoes

question 67

Multiple Choice

A high-mass star near the end of its life undergoes successive cycles of energy generation in its core in which gravitational collapse increases the temperature to the point where a new nuclear fusion cycle generates sufficient energy to stop the collapse. This process does not work beyond the silicon-fusion cycle that produces iron. Explain.

• A) The pressure from high-energy photons and neutrinos at the very high core temperatures reached at this stage of development is finally sufficient to halt the collapse.
• B) Electrostatic forces between the highly charged iron nuclei are sufficient to overcome the collapse and stabilize the stellar core.
• C) Fusion of iron nuclei into heavier nuclei requires energy rather than producing excess energy and therefore will not produce the additional gas pressure to halt the collapse.
• D) Iron nuclei are so large that they occupy all remaining space, so the collapse cannot continue.

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Definitions:

Motor Neurons

Neural cells that make up the route for impulses moving from the brain or spinal cord toward muscles or glands.

Efferent

Referring to nerve fibers that carry impulses away from the central nervous system to effectors, such as muscles or glands.

Afferent

Pertaining to nerve fibers that carry sensory information towards the central nervous system.

Indifferent

Showing no particular interest or sympathy; apathetic or uninvolved emotionally.