Secrets of a dark cloud

Dark clouds are dark because they contain myriads of submicron-sized solid particles - the interstellar dust grains . They also harbour many different species of molecules. They are responsible for the obscuration of light at visible wavelengths. ESO ESO Press Video eso9934 provide a very direct illustration of the dependence of this obscuration on the wavelength (astronomers speak about "dust extinction"): it is higher at shorter wavelengths than at longer ones.

The new data are unique in the sense that it allows astronomers, for the first time, to see through the very centre of a dense molecular cloud, into the cold regions where stars like our Sun will form. We know this because a large number of background stars, not related to the cloud, are seen through the central, most dense regions of B68 in the Ks-image at 2.16 µ&m.

This video provides a direct demonstration of the wavelength dependance of the obscuration in Barnard 68 by means of "cut" and "fade" of the six exposures in different bands,