Helium fusion
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'''Helium fusion''' is a kind of [[nuclear fusion]], with the [[atomic nucleus|nuclei]] involved being [[helium]].
The fusion of helium-4 nuclei ([[alpha particle]]s) is known as the [[triple-alpha process]], because fusion of just two helium nuclei only produces [[beryllium]]-8, which is unstable and breaks back down to two helium nuclei with a half life of 1×10<sup>-16</sup> to 2.6×10<sup>-16</sup> seconds. If the core temperature of a [[star]] exceeds 100 million [[kelvin]]s (100 megakelvins), as may happen in the later phase of [[red giant]]s and [[red supergiant]]s, then a third helium nucleus has a significant chance of fusing with the beryllium-8 nucleus before it breaks down, thus forming [[carbon]]-12. Depending upon the temperature and density, an additional helium nucleus may fuse with carbon-12 to form [[oxygen]]-16, and at very high temperatures, additional fusions of helium to oxygen and heavier nuclei may occur (see [[alpha process]]).
The fusion of helium-3 with itself or with helium-4 occurs during the fusion of hydrogen in main sequence stars (see [[proton-proton chain]]), and is not ordinarily referred to as helium fusion.
==See also==
*[[Fusion power]]
==References==
*{{cite journal |last=Ray |first=Alak K. |authorlink= |coauthors= |year=2004 |month= |title=Stars as thermonuclear reactors: their fuels and ashes |journal=arΧiv e-print |volume= |issue= |pages= |id={{arXiv|astro-ph|0405568}} |url= |accessdate= |quote= }}
[[Category:Nuclear physics]]
[[Category:Nuclear fusion]]
[[ko:헬륨 핵융합]]
[[pt:Processo de combustão do hélio]]
[[zh:氦融合]]