Andromeda Galaxy in visible and infrared light

Herschel’s image of the infrared rings of dust in the Andromeda Galaxy has been colour-coded and superimposed over the optical image. The dust rings neatly fit into the dark lanes of the optical image. The dust appears dark in the visible image because it is not hot enough to shine at visible wavelengths, as stars do. Instead, the dust releases its energy as infrared radiation.