Paolo Padoan

Gas clouds in the Milky Way give birth to stars, and the heaviest among them are true giants. Previously, it was thought that such a star ignites almost instantly, like a light bulb. But new research shows that a star grows gradually, like a snowball rolling down a mountain: the longer it rolls, the bigger it gets. The authors compared two catalogs: bright gas clouds around young stars and the stars themselves.

In cold clouds of interstellar gas, long, dense filaments stretch out. Inside them, like overcrowded incubators, future stars are maturing. For a long time, it was thought that within such filaments, everything was governed by gravity: matter smoothly flows toward the centers, where density increases and eventually a star ignites.