What do infrared observations effectively reveal within a spiral galaxy structure?

Cooler dust that absorbs stellar energy and re-emits it at longer, infrared wavelengths, tracing potential star formation areas.

While visible light highlights the hottest, newest stars, a complete picture of the spiral structure requires looking beyond that range. Dust clouds, which are opaque to visible light, become visible when observed in the infrared spectrum. These lanes of dust and gas absorb energy radiated by nearby, luminous young stars. After absorbing this energy, the cooler dust re-radiates it at much longer, lower-energy infrared wavelengths. Mapping these infrared emissions therefore shows the pathways where the necessary raw material (dust and gas) resides, indicating regions where future star formation is possible, often appearing as warm swathes tracing the compressed zones.