Michigan Test for Teacher Certification (MTTC) Secondary Integrated Science Practice test

What phenomenon is associated with a star's ability to trigger nuclear reactions?

1. Fusion

2. Fission

3. Friction

4. Radiation

The correct answer is: Fusion

The phenomenon associated with a star's ability to trigger nuclear reactions is fusion. In the core of stars, extreme temperatures and pressures enable lighter atomic nuclei, such as hydrogen, to collide and fuse together, forming heavier elements like helium. This process releases a tremendous amount of energy, which is the source of a star's light and heat. Nuclear fusion is fundamental to the lifecycle of stars, as it powers their brightness and influences their evolution. This reaction not only explains why stars shine but also plays a crucial role in the formation of other elements in the universe through subsequent fusion processes in larger stars. The other options relate to different physical processes. Fission involves the splitting of heavy atomic nuclei into smaller parts, which occurs in nuclear reactors rather than in stellar cores. Friction refers to the resistance encountered when two surfaces slide against each other, and it does not relate to nuclear reactions. Radiation is a broader term that includes the emission of energy as electromagnetic waves or as moving subatomic particles, but it is not a direct mechanism for triggering the nuclear synthesis that happens within stars.