AFOQT Practice Test

What are stars primarily made of?

1. Solid rock and metal

2. Gas and plasma

3. Water and ice

4. Dust and debris

The correct answer is: Gas and plasma

Stars are primarily composed of gas and plasma, mainly hydrogen and helium. The immense gravitational forces within stars lead to conditions necessary for nuclear fusion, which occurs in their cores. During this process, hydrogen nuclei (protons) fuse together to form helium, releasing a tremendous amount of energy in the form of light and heat. This energy is what makes stars shine brightly in the universe. While other elements and compounds can be found in stars, the majority of their mass is attributed to the gaseous state of hydrogen and helium, as well as the plasma state that arises at the high temperatures and pressures found in stellar interiors. The other options presented do not accurately capture the primary composition of stars; they refer to materials that are not prevalent in the stellar environment.