Open clusters are formed when a giant molecular cloud collapses under its own weight and quickly fragments into the hundreds, even thousands of stars that make up a star cluster. Observations show that the stars can be either sparsely distributed within the cluster or found in a rather compact formation.

Messier 35 is 2,800 light years away from us and, having been formed only a little more than 100 million years ago, is a fairly young star cluster. All the stars in this cluster have freed themselves from their nascent shroud, a dense molecular cloud, by blowing away most the material leftover from the star forming process. However, some of this material is still present in the immediate neighborhood of these stars. Tiny silicate particles of interstellar dust scatter the light emitted by the bright blue stars in the cluster to produce the diffuse blue fog.