The dust is very rare.
Dust is very rare.
Despite its low abundance, dust is the primary agent which causes the extinction of the light from distant stars. It is the reason that we cannot see more than a few thousasnd or so light years of the Milky Way galaxy in visible light. The gas and dust is not spread uniformly throughout the Milky Way galaxy. It is confined mainly to the disk of the Galaxy , and also, it is not spread uniformly throughout the disk. It is now well-established that these objects are the sites of star formation.