Subrahmanyan Chandrasekhar

If you have heard his name attached to a number — the mass limit beyond which a star cannot hold itself up — that number is the compressed form of a longer argument about how stars are built and how they end. Work on stellar structure, and the limit that now carries his name, is what Subrahmanyan Chandrasekhar is remembered for, and it began as what looked at the time like a modest clarification rather than a break with anything.

Born in Lahore in British India in 1910, he later worked as a mathematician and physicist in the United States. What colleagues noticed early was less spectacle than economy: an argument stripped to the point where a difficult problem became something you could actually handle. Reading, correspondence and travel gave him a comparative view of which problems were worth taking up, and he was willing to press on assumptions that routine practice left alone. Some of his conclusions were contested, and the disputes did useful work — they forced him to state more exactly what he was claiming and where the claim stopped.

In mid-career the range of his subjects widened without the precision loosening. Publications turned insights into techniques other people could repeat, and students and collaborators carried those methods into neighbouring fields. Failed attempts were treated as tests that told him something, not as losses. Institutional positions gave the work reach.

Later he shifted towards synthesis and teaching, passing on what mattered without hardening it into doctrine. His notebooks and drafts survive, and they show how uncertain the route to a clean result actually was — worth knowing, if the finished version has ever made you feel that clarity comes easily to other people. He died in 1995. The durable part of the legacy is less any single result than the habits of attention the work demanded.