[vonobuym] astronomical dust to dust

in astronomy, dust is interstellar material larger than a molecule.  how large is a dust particle permitted to be?

a human corpse floating in space would probably be considered by astronomers as dust.  the proverb "dust to dust" is literally true as scientific jargon.

dust absorbs radiation and reemits with a black body spectrum.  a living human body maintains a constant body temperature (homeostasis), and plants do photosynthesis, so, in general, living things are more complicated than dust in terms of radiation.

can planets and asteroids be dust?  geologically active planets emit radiation unrelated to insolation, and atmospheres turn radiation into weather, kinetic energy.  radiation can also induce phase changes, e.g., comets.  maybe some of these processes have equilibrated.  if none or not much of these processes are happening, is a planet dust?