Aligned grains and scattered light found in gaps of planet-forming disk.

Polarized (sub)millimetre emission from dust grains in circumstellar disks was initially thought to be because of grains aligned with the magnetic field. However, higher-resolution multi-wavelength observations and improved models found that this polarization is dominated by self-scattering at shorter wavelengths (for example, 870 µm) and by grains aligned with something other than magnetic fields at longer wavelengths (for example, 3 mm). Nevertheless, the polarization signal is expected to depend on the underlying substructure, and observations until now have been unable to resolve polarization in multiple rings and gaps.