The Pleiades - Messier 45 

Several of the stars in Pleiads appear surrounded by intricate blue filaments of light. This nebulosity is the result of starlight scattering (reflecting) off minute grains of interstellar dust in the vicinity. The dust particles are inside a cloud of mostly hydrogen gas that the cluster seems to be moving through.(x)

image by: Phillip Pearson,

2 second shutter speeds @ f/2.8, composed of 320 Light frames and 100 Dark frames