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/m³ with each grain having a mass of approximately 10^-17 kg.