Consider a massive, spherical star radiating large amounts of energy in outer space. How does the gravitational field around it behave? Of several possible questions that could be addressed by applying Albert Einstein’s revolutionary theory of general relativity, propounded in 1915, this was an important one. And the solution, known as the Vaidya metric, was first obtained by the mathematician and theoretical astrophysicist P.C. Vaidya (1918-2010), whose birth centenary occurred earlier this week.

The theory of general relativity (GR) is expressed as ten ‘field equations’ valid across the universe, which admit certain exact solutions under certain simplifying assumptions. The first exact solution came soon after the theory was unveiled when the German scientist Karl Schwarzschild described the field around a spherical, non-radiating body in space.

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