Glossary · Vật lý hạt nhân
Nuclear fusion
A reaction in which two light atomic nuclei combine into a heavier nucleus and release energy. It needs extremely high temperatures so the nuclei can overcome their electrical repulsion. It is what powers the Sun and other stars.
Energy is released because the resulting nucleus has less mass than the nuclei that went into it, and that missing mass corresponds to energy through E = mc². Nuclei are all positively charged and repel one another; only when they collide at very high speeds, that is, at extremely high temperatures, can they overcome this repulsion and fuse.
In the Sun's core, immense pressure and temperature squeeze hydrogen nuclei together to form helium. The energy released heats the star and keeps it from collapsing under its own weight. In massive stars the chain goes on through progressively heavier elements until silicon fuses into iron.
Projects such as ITER are working on sustaining fusion on Earth; in a laboratory device the temperature required is far higher than in the Sun's core.