Cosmic dust is
dust which exists in
space. Most cosmic dust particles are between a few
molecules to 0.1
µm in size. A smaller fraction of all dust in space consists of larger refractory minerals that condensed as matter left the stars. It is called "stardust" and is included in a separate section below. The dust density in the local interstellar medium of the
Local Bubble is approximately 10
-6 × dust grain/m
3 with each grain having a mass of approximately 10
-17 kg.