nanodust

Nanodust refers to solid particles with dimensions on the nanometer scale, typically less than 100 nanometers. In astrophysics, nanodust denotes interstellar and interplanetary grains of a few nanometers to tens of nanometers that influence light extinction and emit in the infrared. In materials science, nanodust is also used to describe engineered nanoscale particles used in research and industry.

In the interstellar medium, nanodust includes carbonaceous grains, very small grains, and polycyclic aromatic hydrocarbons; they contribute to ultraviolet extinction and to characteristic infrared emission bands near 3 to 12 micrometers. These small grains affect the heating of interstellar gas and the chemistry of molecular clouds, and they participate in processes such as charge exchange and coagulation into larger particles.

Formation and processing of nanodust occur in multiple environments. They can condense in cooling stellar outflows from asymptotic giant branch stars or supernova ejecta, and they can also form by fragmentation of larger grains in shocks or intense radiation fields. Once formed, nanodust is shaped by irradiation, collisions, magnetic forces, and accretion in dense regions, influencing their size distribution and composition.

Detection and study rely on infrared spectroscopy, extinction curves, and, for in situ measurements, spacecraft detectors that register impact ionization from incoming nano-dust. These methods yield information on abundance, composition, and flux, along with the velocities of nanometer-scale grains.

Applications and relevance extend to both astronomy and technology. In nanotechnology, engineered nanodust particles are developed for electronics, catalysis, and delivery systems, while astrophysical nanodust research helps illuminate interstellar chemistry, star formation, and planetary system evolution. Safety and environmental considerations apply to manufactured nanomaterials.