Neutronium Core?
Hi LJK
Ever read the theories of Oliver Manuel? He proposes the Sun is a neutron star that has choked on its own ash, thus the Sun isn't mostly hydrogen - as solar modellers assume to great success - but is in fact made of iron and a core of neutronium. All based on curious isotopic signatures.
Personally I think he's a crank, but he's an informed crank - actually knows physics, rather than being an ignoramus like Velikovsky. Every new isotope and solar modelling discovery nibbles away at Manuel's claimed anomalies.
Adam