ISPH Nuclear Energy Practice Test

What is the minimum core temperature required for nuclear fusion to occur in stars?

1 million Kelvin 10 million Kelvin 100 million Kelvin 1000 Kelvin

Correct Answer:

10 million Kelvin

Explanation:

Fusion in stars requires nuclei to collide with enough energy to overcome their electrostatic repulsion, and the reaction rate increases sharply with temperature. In stellar cores, temperatures reach a few tens of millions of kelvin, which is enough for protons to fuse mainly through the proton-proton chain (for Sun-like stars) or the CNO cycle (in more massive stars). The proton-proton chain becomes efficient around about ten million kelvin, and the Sun’s core is even hotter, around 15 million kelvin, sustaining the fusion that powers the star. So the minimum core temperature needed for fusion to occur at an appreciable rate is about ten million kelvin. The other options are far too low to overcome the Coulomb barrier, or higher than the threshold needed.

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