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The Chandrasekhar limit is the maximum mass at which gravity allows a white dwarf to remain stable, i.e., above this mass, it will collapse into a neutron star. The limit assumes gravity is not counteracted by a magnetic field or by rotation: if either is present, the mass can possibly be somewhat larger. The limit is the point at which gravity overcomes electron degeneracy pressure, the mechanism that supports a white dwarf. Its current estimate is 1.44 solar masses. Such a limit was first calculated in 1929 and 1930 by Edmund Clifton Stoner and Wilhelm Anderson, and later was refined by Subrahmanyan Chandrasekhar. Stars losing their thermonuclear-generated heat and pressure that remain sufficiently massive (after ejecting mass) to exceed this limit collapse into neutron stars or black holes. White dwarfs accreting matter can reach this limit and collapse as well. Some of these collapses result in various types of supernovae.
The analogous limit above which a neutron star must further collapse (into a black hole) is the Tolman-Oppenheimer-Volkoff limit (TOV).