What is the name of the process by which energy is released when two nuclei join together?

The process by which energy is released when two atomic nuclei combine is known as fusion. In fusion, light nuclei, typically isotopes of hydrogen, merge under extreme pressure and temperature to form a heavier nucleus, such as helium. This reaction is accompanied by a significant release of energy, which is the principle behind the energy produced by stars, including our sun.

Fusion is fundamentally different from fission, which involves the splitting of a heavy nucleus into lighter nuclei, releasing energy in the process. Conduction and radiation are modes of heat transfer rather than nuclear processes. Thus, the identification of fusion as the correct answer highlights the principle of energy generation through the combining of atomic particles under the right conditions. This understanding is crucial when examining energy production in both natural and controlled environments, such as nuclear reactors and the potential for fusion energy development.