May be a beginner's question but I couldn't find the answer anywhere.
Given a supernova event and the cloud left by it, why does a new star coalesce with a disproportionally higher hydrogen(and helium) content compared to the matter left on it's vicinity?
Shouldn't gravity form bodies(maybe stars still) with all, or most of, the heavier elements and leave the hydrogen and helium in the vicinity instead?
I would also appreciate any book indications on that matter.