The nuclear fusion process in evolved stars where helium nuclei combine to form heavier elements like carbon and oxygen. This occurs at much higher temperatures than hydrogen burning, typically above 100 million Kelvin.
From Greek 'helios' (sun, where helium was first detected) + 'burning' (from Old English 'byrnan'). The term developed in the mid-20th century as astronomers understood stellar nucleosynthesis processes.
Helium burning is stellar alchemy at its finest - it's how stars transform the 'ash' of hydrogen fusion into the carbon and oxygen that make planets and life possible! This process requires such extreme temperatures that it only happens in the cores of evolved stars, creating the heavy elements that weren't made in the Big Bang.
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