Picture NGC 891 shows the movement of dust in the galaxy. The blue areas correspond to the places where hot and young stars have formed recently. Yellow facets on the path of the dust are caused by the fact that the blue light is absorbed by the dust itself. This phenomenon is observed in our galaxy too. One can also see distant separate galaxies far away from NGC 891. The Center's answer: This is a process of dissolving of the source of formation of Mothers - a stage of star formation close to the end.