If astronomers were limited to visible light, chances are no one would have realized that Maffei 2 was a galaxy. This image shows identical exposures of Maffei 2 and NGC 1300, a barred galaxy of similar size and distance. From Earth, the two objects appear very different from one another: because of dust, Maffei 2 is a faint red smudge; NGC 1300, on the other hand, is bright and its spiral arms are easily visible. 
    Dust is common in galaxies and can be a real hindrance to astronomers. Look at the sky on a dark night and you may see the faint band of light overhead that is our inside-out view of the Milky Way. But the band is not regular; mixed with the light are many dark patches. These are clouds of dust