Worked example - what becomes of a 1.6 solar-mass stellar core? After a Sun-like star sheds its envelope, suppose the leftover carbon-oxygen core weighs 1.6 M_sun. Step 1: compare with the Chandrasekhar limit, 1.4 M_sun. Step 2: 1.6 > 1.4, so electron degeneracy pressure cannot support it - no stable white dwarf is possible. Step 3: the core collapses further. If it is in a binary and accreting, it may explode as a Type Ia supernova; a single core this massive at the end of a massive star's life collapses to a neutron star (if below ~3 M_sun). Moral: 1.4 M_sun is the strict ceiling for white dwarfs.