A summary of information about interstellar dust and its roles in the Milky Way galaxy
| Origin | Circumstellar envelopes of cool, evolved stars |
| Ejecta from supernovae | |
| Signature | Extinction and polarization of starlight |
| Inferences from modelling interstellar extinction | Caused by small dielectric particles |
| Typical range of grain radii: a ∼ 5 nm–0.5 µm | |
| Typical size distribution: number in range a → a + da is dn ∼ a−3.5da | |
| Composition | Silicate and carbon solids, either distinct or combined; usually amorphous, plus PAH molecules |
| Role in interstellar chemistry | Surface reactions, especially H2 formation |
| Role in solid-state chemistry | Accumulation of simple mixed ices on surfaces of dust particles |
| Processing of mixed ices to more complex species | |
| Role in evolution of the galaxy | Essential functions in star and planet formation |
| Origin | Circumstellar envelopes of cool, evolved stars |
| Ejecta from supernovae | |
| Signature | Extinction and polarization of starlight |
| Inferences from modelling interstellar extinction | Caused by small dielectric particles |
| Typical range of grain radii: a ∼ 5 nm–0.5 µm | |
| Typical size distribution: number in range a → a + da is dn ∼ a−3.5da | |
| Composition | Silicate and carbon solids, either distinct or combined; usually amorphous, plus PAH molecules |
| Role in interstellar chemistry | Surface reactions, especially H2 formation |
| Role in solid-state chemistry | Accumulation of simple mixed ices on surfaces of dust particles |
| Processing of mixed ices to more complex species | |
| Role in evolution of the galaxy | Essential functions in star and planet formation |