Infrared dark clouds are cold, dense molecular clouds cores seen in silhouette against the bright diffuse mid-infrared emission of the Galactic plane.
A particular striking example is G11.11-0.11 seen below in extinction at 8 microns and 2MASS Ks band and in emission at 850 microns.
|8 micron image of G11.11-0.11 from MSX. It is seen in extinction against the bright diffuse mid-infrared emission of the Galactic plane.||Ks image of G11.11-0.11 from 2MASS. It is seen in extinction against the numerous stars in the Galactic plane||850 micron image of G11.11-0.11 from SCUBA at the JCMT. The bulk of the IRDC can be seen as a fainter envelope of emission surrounding some brighter regions. The bright region in the center of the image contains a suspected massive class 0 protostar.|