  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.
