Principal Nuclear Fusion Process in the Sun

Principal Nuclear Fusion Process in the Sun

The Proton-Proton Chain Reaction

• The most dominant nuclear fusion process in the Sun, responsible for about 99% of its energy, is the proton-proton chain reaction.
• This process occurs in three main stages.
• In the first stage, two protons come together to form a heavier particle known as a deuteron.
• Alongside the deuteron, a positron and a neutrino are also produced.
• The positron immediately annihilates with an electron, releasing gamma radiation.

Role of Deuteron

• In the second stage, a deuteron fuses with another proton to create a helium-3 nucleus.
• A gamma photon is released during this stage of the reaction.
• The helium-3 nucleus is unstable and does not last long.

Formation of Helium-4

• The final stage of the proton-proton chain reaction involves the fusing of two helium-3 nuclei to form a helium-4 nucleus.
• During this process, two protons are released, which can participate in future proton-proton chain reactions.
• The energy released in this step comes out primarily in the form of kinetic energy of the helium-4 nucleus and the two protons.

Energy Output

• The energy produced by the proton-proton chain reaction is eventually carried to the Sun’s surface in the form of light and heat.
• The process of energy transfer from the Sun’s core to its surface takes approximately a million years.
• These reactions take place countless times each second, converting millions of tons of matter into energy.
• This process is essentially the source of sunlight and the reason life is possible on Earth.

Neutrinos

• Neutrinos are weakly interacting particles produced as a by-product in the first step of the proton-proton chain reaction.
• Because they’re weakly interacting, many neutrinos escape the Sun and reach Earth undetected — these are known as ‘solar neutrinos’.
• Studying solar neutrinos gives scientists valuable information about processes occurring inside the Sun.