19 October

1910: On 19 October 1910, Subrahmanyan Chandrasekhar was born.

Chandrasekhar was an Indian-born American astrophysicist who (with William A. Fowler) won the 1983 Nobel Prize for Physics for formulating the currently accepted theory on the later evolutionary stages of massive stars.

He was one of the first scientists to combine the disciplines of physics and astronomy. Early in his career he demonstrated that there is an upper limit, now called the 'Chandrasekhar limit', to the mass of a 'white dwarf' star.

A white dwarf is the last stage in the evolution of a star such as the Sun. When the nuclear energy source in the centre of a star such as the Sun is exhausted, it collapses to form a white dwarf. It shows that stars much more massive than the Sun must either explode or form black holes.