A vast stellar nursery 14,000 light years away has been hiding behind a thick cloud of dust. It is one of the biggest in our galaxy, and may offer insight into how these objects can grow so big.

The stellar nursery, called CTB 102, is home to perhaps thousands of newborn stars. Measuring 380 light years across, the nursery is a so-called H II region, where the hottest and most massive stars have stripped hydrogen gas of its electrons. The most famous of these regions is the Orion nebula, but CTB 102 is over 10 times its size.

CTB 102 has eluded recognition because it is in the Perseus arm, the spiral arm of the Milky Way next out from ours, where dust blocks visible light. Its size and distance from Earth were unveiled by mapping radio waves emitted from hydrogen gas.

The nursery likely grew so large because winds from its hottest stars caused the gas and dust that hatched them to spread outwards. "Massive stars are principal sculptors of gas and dust," says team member Charles Kerton of Iowa State University in Ames.