While the Sun is an excellent starting point in a quest to understand magnetism, the authors of today’s paper want more. They take advantage of something only relatively cool stars can have in their atmospheres to study magnetic fields: molecules in starspots.
Polarimetry is one of the handful of fundamental methods used to study incoming radiation and can provide substantial clues to the nature of the source. Polarimetry is used to extract information such as the strength of magnetic fields in the interstellar medium (ISM), provide evidence for inflation by observations of the CMB polarization, and motivate a unified model for active galactic nuclei (AGN).