Proton-proton cycle

Definition

The proton-proton cycle is a series of nuclear fusion reactions that convert hydrogen into helium, releasing energy. It is the dominant energy source in stars like the Sun.

5 Must Know Facts For Your Next Test

1. The proton-proton cycle consists of three main steps, producing helium-4 from four protons.
2. It releases energy in the form of gamma rays, positrons, and neutrinos.
3. Proton-proton fusion occurs at temperatures around $10^7$ Kelvin.
4. The cycle produces about 26.7 MeV of energy per complete reaction.
5. Neutrinos produced in the proton-proton cycle are crucial for solar neutrino experiments.

Review Questions

• What are the three main steps involved in the proton-proton cycle?
• What kind of particles and radiation are released during the proton-proton cycle?
• Why is the proton-proton cycle important for understanding how stars like the Sun generate energy?

Related terms

Nuclear Fusion:

A nuclear reaction where atomic nuclei combine to form a heavier nucleus, releasing energy.

Helium-4: A stable isotope of helium produced as a final product in the proton-proton cycle.

Neutrino:

A nearly massless subatomic particle released during nuclear reactions such as those in the proton-proton cycle.