Although interstellar dust constitutes only about 1 percent of the matter in the Milky Way, it is the main source of Infrared radiation in this image. Grains of interstellar dust are tiny (about .005 to .2 micrometers); even so they have made it difficult for astrono- mers to observe and interpret radiation from other parts of the Milky Way. Dust absorbs many wavelengths of visible light, and some of the obscured areas, such as the Galactic Center, are of great interest.
The colors in this image tell us much about the physical conditions in our galaxy and solar system. The red radiation (100 micrometers) is largely from the galactic disk. The blue radiation (12 micrometers) is thought to be from two sources:
