1931 – USA

‘The maximum possible mass of a white dwarf star is 1.4 times the Sun’s mass’

Early library photograph of SUBRAHMANYAN CHANDRASEKHAR (1910-95)


The Chandrasekhar limit is a physical constant.
It is the greatest mass a white dwarf star can have before it goes supernova, approximately 1.44 solar masses. Chandrasekhar showed that it is impossible for a white dwarf star, which is supported solely by electron degeneracy pressure, to be stable if its mass is greater than 1.44 times the mass of the Sun. If such a star does not completely exhaust its thermonuclear fuel, then the limiting mass may be slightly larger.
Above this limit a star has too much mass to become a white dwarf after gravitational collapse. A star of greater mass will become a neutron star or a black hole.


The radius of a black hole is the radius of the event horizon surrounding it. This is the Schwarzschild radius, after the German astronomer Karl Schwarzschild (1873-1916) who in 1916 predicted the existence of black holes.
The Schwarzschild radius is roughly equal to three times the weight of the black hole in solar masses. A black hole weighing as much as the Sun would have a radius of 3 kilometres, one with the mass of the Earth would have a radius of only 4.5 millimetres. A black hole’s effects occur within ten Schwarzschild radii of its centre.

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