A mystery in astronomy is how supermassive black holes grew so big, so quickly. Astronomers have looked for quasars, actively feeding supermassive black holes, as a way to measure how much new material they’re accumulating, contributing to their growth. They studied nebulae near the quasars that light up when the quasar is releasing radiation and found that many of the farthest quasars have only been active for a few hundred thousand years, not long enough to grow.