Can we observe dust moving? In other words, can we see the proper motions of the ISM? It should be moving around relative to us. There is some known about the shell of ISM around the Sun, but mystery remains about the small-scale structure of the ISM throughout the Milky Way.

There are 2 ways to approach this problem:

1. Direct observation

  • requires high-res molecular (radio/mm) maps over time, or high-res IR emission maps
  • most current maps available in literature probably not sufficient over large ares, and certainly not stable over time.
  • most IR surveys do not have the required resolution, but future missions would
  • radio/mm probably has the resolution and stability needed to directly track the motions of the near-field ISM
  • gives some info about density structure, but lots of info about kinematics and dynamical structure of the ISM

2. Variations of extinction, E(B-V)

  • probably easier to detect in the blue optical, can possibly be done from large surveys determining the extinction of distant stars shining through near-field ISM that is moving
  • gives less specific detail on the motions of the ISM relative to the Sun
  • does give info on the density structure of the ISM on potentially very small scales
  • people have started to compare dust extinction maps, e.g. Planck vs WISE which may be a way forward