Oppenheimer’s brief advance into astrophysics began with a 1938 paper about neutron stars, which continued in a 1939 installment that further incorporated the principles of Einstein’s general theory of relativity. He then published a third paper on black holes on September 1st, 1939—but at the time, it was scarcely noticed because this was the very day Germany invaded Poland, launching World War II. Oppenheimer never wrote on the topic again.

Even if it hadn’t been overshadowed by war, Oppenheimer’s work on neutron stars and black holes “was not understood to be terribly significant at the time,” says Cathryn Carson, a historian of science at the University of California, Berkeley.

Each paper was written with a different member of the swarm of graduate students that Oppenheimer carefully cultivated. These protégés facilitated his ability to jump between research topics—and ultimately, helped him develop some of his most important contributions to physics.

Oppenheimer’s climactic third paper, written with his student Hartland Snyder, explores the implications of general relativity on the universe’s most massive stars. Although the physicists needed to include some assumptions to simplify the question, they determined that a large enough star would gravitationally collapse indefinitely—and within a finite amount of time, meaning that the objects we now know as black holes could exist.

Internet: <scientificamerican.com> (adapted)