Question

Which of the following must occur for a star's core to reach equilibrium after an initial change in fusion rate?

A. If the fusion rate initially decreases, then the core expands.
B. If the fusion rate initially increases, then the core expands.
C. If the fusion rate initially decreases, then the core contracts.
D. If the fusion rate initially increases, then the core contracts

Answer 1

For a star's core to reach equilibrium after an initial change in fusion rate, it will contract if the fusion rate decreases and expand if the fusion rate increases. The core's adjustments help maintain the delicate balance between gravitational forces and nuclear fusion.

Step-by-step explanation:

For a star's core to reach equilibrium after an initial change in fusion rate:

• If the fusion rate initially decreases, then the core contracts (C). This contraction increases the core's temperature and the fusion rate, thus restoring equilibrium.
• If the fusion rate initially increases, then the core expands (B). The expansion cools down the core, reducing the rate of fusion and thus bringing the star back to equilibrium.

Stars remain stable as long as they can maintain nuclear reactions against gravitational collapse. When the fuel for fusion is depleted, gravity causes the core to contract and heat up. For stars with iron cores, fusion stops, leading to a supernova.