Supermassive black holes—millions to billions times more massive than the Sun—reside at the center of almost every galaxy, and they power distant, bright quasars that already existed when the universe was only a billion years old. But understanding how such supermassive black holes could form so early in the universe is a challenge. Some theoretical models suggest that they could have originated as supermassive stars, comprising 10 000 or more solar masses, that collapse into black holes and then grow through subsequent accretion and galaxy mergers to reach the observed sizes. (For more on the earliest stars, see the article by Tom Abel, Physics Today, April 2011, page 51.)
New supercomputing simulations by Ke-Jung Chen (University of California, Santa Cruz) and colleagues have revealed that primordial stars of around 55 000 solar masses might not all end up as black holes, as models predict—they can instead die as...
