What causes the initial shutdown of fusion in the core when a Sun-like star enters the red giant phase?
Answer
The temperature and pressure conditions required for hydrogen fusion are no longer met in that specific region.
Fusion stops in the core because once the hydrogen is converted to helium ash, the resulting region lacks the necessary temperature and pressure to sustain hydrogen fusion.
Frequently Asked Questions
What causes the initial shutdown of fusion in the core when a Sun-like star enters the red giant phase?What is the phenomenon responsible for powering the dramatic expansion of a star into a red giant?How does the energy output during the hydrogen shell burning phase compare to the star's main-sequence phase?What state supports the inert helium core of a low-mass star while it contracts before helium ignition?Approximately what minimum temperature is required for helium fusion (the triple-alpha process) to begin in the core?What happens to the inert helium core immediately after core hydrogen fusion ceases?What marks the definitive end of fusion for the core of a low-mass star ($\lesssim 2.2 M_\odot$) after the red giant phase?How is the energy generation process characterized during the main sequence phase?For very massive stars, what event signifies the point where fusion truly ends catastrophically within the core?What is the primary physical mechanism causing the star's outer envelope to swell hundreds of times its original radius during the red giant phase?