Inferring the temperature structure of circumstellar disks from polarized emission
Polarized light is a familiar phenomenon because the scattering or reflection of light results in one of its two components being preferentially absorbed. The majority of sunlight on Earth, for example, is preferentially polarized due to scattering in the atmosphere (this helps make polarized sunglasses effective). Electromagnetic radiation from astrophysical sources can also be polarized, typically because of scattering from elongated dust grains that are aligned with each other by the local magnetic fields. These fields are thought to play a major, perhaps even a dominant role in controlling the shapes and motions of interstellar gas clouds and are extremely difficult to measure directly. Observations of polarization by dust grains offer a unique way to probe the magnetic fields.