DrSubrahmanyan Chandrasekhar

In the summer of 1930 a nineteen-year-old from Madras boarded a steamship for England, bound for graduate study at Cambridge, and spent the long voyage doing physics. By the time the ship docked he had worked out something that would reshape astronomy: there is an upper limit to the mass of a white dwarf star. Beyond about 1.4 times the mass of the Sun, he calculated, the star cannot hold itself up against its own gravity, and must collapse into something far stranger. That number is now known to every astrophysicist as the Chandrasekhar limit, and it opened the road to neutron stars and black holes.

A scientific family

Subrahmanyan Chandrasekhar — "Chandra" to colleagues for the rest of his life — was born on 19 October 1910 in Lahore, into a Tamil Brahmin family of high intellectual distinction. His uncle was C. V. Raman, who in 1930, the very year of Chandra's voyage, won the Nobel Prize in Physics for the Raman effect — the first Asian to win a Nobel in the sciences. The young Chandra was educated at Presidency College in Madras, took his degree in physics, and won the scholarship that sent him to Trinity College, Cambridge.

The clash with Eddington

His shipboard calculation should have made his early reputation. Instead it nearly broke him. Through the early 1930s Chandrasekhar developed the theory of white-dwarf collapse into a complete and rigorous account. In 1935, at a meeting of the Royal Astronomical Society in London, he presented it — and was ambushed. Sir Arthur Eddington, the most celebrated astrophysicist alive and a man Chandra had admired and trusted, rose immediately after and publicly ridiculed the result as physically absurd, declaring there must be a law of nature to prevent a star from behaving so preposterously. Eddington's authority was immense, and the astronomy establishment largely deferred to him. The episode — sharpened by the imbalance of age, eminence and, unmistakably, race — was devastating. Chandrasekhar was right and Eddington was wrong, as the decades would prove, but the young Indian could not win a public argument against the field's reigning giant, and the wound helped drive him out of England.

Fifty-eight years at Chicago

In 1937 Chandrasekhar joined the University of Chicago, and there he stayed for fifty-eight years, based partly at the Yerkes Observatory. He built a body of work of legendary range and rigour, moving methodically from one great problem to the next and, characteristically, writing a definitive monograph on each before moving on: stellar structure, stellar dynamics, radiative transfer, the equilibrium of rotating fluids, hydrodynamic and hydromagnetic stability, the mathematical theory of black holes, and, at the end, the collision of gravitational waves. For nearly two decades he also edited The Astrophysical Journal, the field's leading publication, transforming it into an international institution and imposing on it his own exacting standards.

The hundred-mile classroom

The story astronomers tell most often about him concerns a class of two. In the early 1940s Chandrasekhar drove roughly a hundred miles each way, through Wisconsin winters, from Yerkes Observatory to the Chicago campus to teach an advanced course to just two enrolled students, Tsung-Dao Lee and Chen-Ning Yang. Both went on to win the Nobel Prize in Physics — in 1957, more than a quarter-century before their teacher won his. The anecdote is told partly for its irony and partly for what it says about his seriousness: the course mattered, so he taught it, two students or two hundred.

The Nobel, at last

His own Nobel Prize in Physics came in 1983, awarded for his theoretical studies of the structure and evolution of stars — more than half a century after the calculation on the ship. He accepted it with characteristic reserve, and with pointed generosity toward the young man he had once been, whose work had waited so long for vindication. He became the second Nobel laureate in a single Indian family, after his uncle Raman.

Why the Roll remembers him

Chandrasekhar died in Chicago in 1995. After his death, NASA named its flagship X-ray space telescope the Chandra X-ray Observatory in his honour — so the diaspora's first great scientist now, in a sense, orbits the Earth studying the very collapsed stars and black holes his mathematics predicted. He belongs on this Roll as the pioneer: the first person of Indian origin to build a towering scientific career entirely abroad, in the face of a establishment that first humiliated and then, decades late, honoured him. His life carries a hard lesson the diaspora has learned many times over — that being right is sometimes not enough against the authority and prejudice of the moment — and a consoling one, that the mathematics endures long after the men who mocked it are forgotten.

Truth and beauty

Beneath the mathematics lay a philosophy. Chandrasekhar believed, and argued in a celebrated series of lectures published as Truth and Beauty, that the deepest scientific theories possess an aesthetic rightness akin to great art, and he drew explicit parallels between the beauty of physics and that of Shakespeare, Beethoven and the sculptures he loved. His final major work, completed in his eighties, was a labour of devotion of a different kind: a book-length commentary rendering the geometry of Newton's Principia accessible to the modern reader, a homage from one of the twentieth century's great mathematical physicists to the founder of the discipline.

The long partnership

He was married for nearly seventy years to Lalitha Doraiswamy, a fellow physics student he had known in Madras, who joined him in America and whose support underpinned his long, monastic devotion to work. Colleagues remembered his exacting standards, his formal courtesy, and the disciplined rhythm of a life organised entirely around research and the journal he edited. When he died in Chicago in 1995, he left a body of work of almost unmatched breadth and rigour, and a lesson the diaspora has taken to heart many times over: that authority and prejudice can delay recognition for decades, but cannot, in the end, overturn a correct calculation. NASA's naming of its great X-ray observatory Chandra ensured that his name now travels in orbit, studying the collapsed stars and black holes his shipboard mathematics first predicted.