Experimental evidence of neutrinos produced in the CNO fusion cycle in the Sun (Nature cover story)

For most of their existence, stars are powered by fusion of hydrogen into helium via two processes that are well understood theoretically: the proton–proton chain, dominant in relatively small stars like our Sun, and the Carbon–Nitrogen–Oxygen cycle, which is prevalent in bigger, more massive stars. Borexino got the first experimental evidence of neutrinos emitted by the CNO cycle in the Sun core.