It is stuff left over from a previous star's supernova. That's the only way anything heavier than iron and nickel gets produced. It is a small amount, but it'

It is stuff left over from a previous star's supernova. That's the only way anything heavier than iron and nickel gets produced. It is a small amount, but it's more visible than its raw proportion, because it gets suspended in the stellar atmosphere, because the large atoms get hit by a lot of radiation pressure. The point of this is that we don't need to rethink heavy element production (or at least not by much), because known processes suffice.