Mengke Zhao

NGC 3627, a spiral beauty in the constellation Leo, harbors a trail that fits no standard scenario. A narrow band of cold gas, a molecular trail, stretches more than 8 kiloparsecs (thousands of parsecs, each about 3260 light-years) with a width of about 200 parsecs. That is like a thread as long as a football field and as thick as a pencil.

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.