Dear Michael, All the big stars, i.e. those with a mass exceeding the sun’s mass by a factor of 1.3, gain most of their energy by a hydrogen-fusion reaction that involves a catalytic cycle, known as the Bethe-Weizsäcker or CNO-cycle. During this reaction cycle, protons (i.e. hydrogen nuclei) are added four times into a cycling reaction that converts carbon through… (more…)