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What role do gamma rays play in fusion reactions inside stars?

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laser-activated fusion — nuclear fusion Interior of the U.S. Department of Energy's National Ignition Facility (NIF), located at Lawrence Livermore National Laboratory, Livermore, California. The NIF target chamber uses a high-energy laser to heat fusion fuel to temperatures sufficient for thermonuclear ignition. The facility is used for basic science, fusion energy research, and nuclear weapons testing.

In stellar fusion reactions, gamma rays serve as a mechanism for carrying away a portion of the energy released during nuclear transformations.1

In the proton-proton cycle, for example, the capture of a proton by a deuterium nucleus to form helium-3 results in the emission of a gamma-ray photon. Similarly, in the CNO cycle, gamma rays are emitted during various stages of proton capture, such as when carbon-12 or nitrogen-13 nuclei interact with protons.123

Beyond their role in specific reaction steps, gamma rays are significant to the structure of stars because they represent the initial form of energy generated in the core. This radiation must be transported outward toward the star's surface. In stars like the Sun, this energy begins as gamma rays near the core and is gradually "softened"—meaning the wavelengths increase—as it works its way through the stellar interior over approximately a million years, eventually emerging as the light and heat we observe.4