If the mass of a star’s iron core exceeds the Chandrasekhar limit (but is less than 3 M Sun ), the core collapses until its density exceeds that of an atomic nucleus, forming a neutron star with a typical diameter of… Stars with masses of 8 M Sun or less can lose enough mass to become white dwarfs, which have masses less than the Chandrasekhar limit (about 1.4 M Sun ).

In a massive star, hydrogen fusion in the core is followed by several other fusion reactions involving heavier elements. Just before it exhausts all sources of energy, a massive star has an iron core surrounded by shells of silicon, sulfur, oxygen, neon, carbon, helium, and hydrogen.

Chandrasekhar limit (but — less than 3 M Sun ), the core collapses until its density exceeds that of an atomic nucleus, forming a neutron star with a typical diameter of…. neutron star — a compact object of extremely high density composed almost entirely of neutrons. core — followed by several other fusion reactions involving heavier elements. Chandrasekhar limit — the upper limit to the mass of a white dwarf.