Nanodust in the Interstellar Medium in Comparison to the Solar System

Abstract

Nanodust, which undergoes stochastic heating by single starlight photons in the interstellar medium, ranges from angstrom-sized large molecules containing tens to thousands of atoms (e.g. polycyclic aromatic hydrocarbon molecules) to grains of a couple tens of nanometers. The presence of nanograins in astrophysical environments has been revealed by a variety of interstellar phenomena: the optical luminescence, the near- and mid-infrared emission, the Galactic foreground microwave emission, and the ultraviolet extinction which are ubiquitously seen in the interstellar medium of the Milky Way and beyond. Nanograins (e.g. nanodiamonds) have also been identified as presolar in primitive meteorites based on their isotopically anomalous composition. Considering the very processes that lead to the detection of nanodust in the ISM for the nanodust in the solar system shows that the observation of solar system nanodust by these processes is less likely.