11 The Chandrasekhar Limit
Life as we know it is based on the element carbon, but life also requires a large variety of other, heavier atoms. There is only one process in the universe that produces these heavier elements, and that is a supernova, the explosion of a giant star. A supernova explosion produces all those heavier elements and scatters them throughout the universe, enabling planets to form and life to evolve. Supernovas are rare but spectacular. The supernova that appeared in the sky in 1987 actually happened more than 150,000 light years from earth, but was still visible to the naked eye.
The size of a star determines its fate. Stars the size of the sun live relatively quiet lives (though billions of years from now the sun will expand and engulf the earth). Stars slightly larger than the sun will become white dwarves, intensely hot but small stars that will cool slowly and die. However, if a star exceeds a certain mass—the Chandrasekhar limit—then it is destined to become a supernova.
The Chandrasekhar limit is approximately 1.4 times the mass of the sun. Extraordinarily, Subrahmanyan Chandrasekhar discovered this as a 20-year-old student by combining the theories of stellar composition, relativity and quantum mechanics during a trip on a steamship from India to England.