Complex sentence: Carbon detonation generally occurs when the accreted matter pushes the white dwarf's mass close to the Chandrasekhar limit of roughly 1.4 solar masses where gravity can overcome the electron degeneracy pressure which had prevented the star from collapsing during its lifetime.
Split into simpler sentences: Carbon detonation generally occurs at the point when the accreted matter pushes the white dwarf's mass close to the Chandrasekhar limit of roughly 1.4 solar masses. This is the mass at which gravity can overcome the electron degeneracy pressure which had prevented the star from collapsing during its lifetime.