V. M. Rivilla

In a cold gas cloud right at the center of our Galaxy, designated G+0.693-0.027, hides a true chemical laboratory. There, far from stars, on the surfaces of tiny dust grains, about the size of smoke particles, atoms stick together into molecules, like dough on a kitchen counter.

In dark, cold clouds of interstellar gas, astronomers have for several years been spotting aromatic molecules — compounds built around a benzene ring (a hexagon of carbon atoms), like the benzene we know. One such substance, benzonitrile (benzene with a cyano group attached), had only been found in very calm and cold places, like the Taurus cloud.

In an oven, a huge loaf of bread is baking. Inside the dough, there is a tiny, hottest spot: that's where the future loaf begins to rise. A hot molecular core (a region the size of the Solar System, where gas is heated to hundreds of degrees and compressed to billions of times the density of ordinary clouds) works in much the same way.