In the Sun's core, light is produced through a process called nuclear fusion. The Sun primarily consists of hydrogen gas, and in its core, the temperature and pressure are incredibly high. These conditions are ideal for nuclear fusion to occur.
The process begins with the fusion of hydrogen nuclei, or protons, to form helium nuclei. This reaction, known as the proton-proton chain, involves several steps. In the first step, two protons combine to form a deuterium nucleus (one proton and one neutron) through a weak nuclear force interaction. This step releases a positron (a positively charged electron) and a neutrino as byproducts.
In the next step, a deuterium nucleus fuses with another proton to produce a helium-3 nucleus. This reaction releases a gamma ray photon, which is a high-energy packet of light. The helium-3 nucleus can further combine with another helium-3 nucleus to form helium-4, releasing two protons in the process.
The fusion reactions in the Sun's core continuously release huge amounts of energy in the form of gamma ray photons. However, gamma rays are absorbed and scattered by the dense matter in the core. As a result, it takes a long time for the gamma rays to reach the Sun's surface, where they are finally emitted as visible light, along with other forms of electromagnetic radiation.
The light generated in the Sun's core gradually makes its way through the various layers of the Sun, undergoing absorption, re-emission, and scattering. It eventually reaches the Sun's photosphere, the visible surface, and is released into space as sunlight.