Why do nuclei of elements heavier than hydrogen not fuse in main sequence stars?
In main sequence stars the gravitational force pulling itself together is huge. But it stabilizes because once it gets to a certain point, hydrogen starts fusing ( but there are also failed stars he cannot produce fusion because their gravity is not strong enough to pull them together tight enough to create any fusion) and pushing outward against the pull of gravity. The core is not tight enough or hot enough to create fusion for any elements except hydrogen, which in turn creates helium. But once the “fuel” (hydrogen) runs out, fusion can no longer take place, so there is no force pushing outward against gravity anymore, causing the star to implode (and goes supernova). The star then shrinks down and collapses until the core of this “re-born” star is now tight enough and hot enough to burn the helium created from the last cycle. This cycle now repeats through oxygen, nitrogen, etc. until we get to the point where we are only left with iron. Iron cannot be “burned” by fusion because it
