Polarization: The Second Stellar Spectrum

Ken Gayley

University of Iowa

Astronomical images sort light by direction and color, and spectra sort it into finer wavelength bins, thereby using light to learn about our universe. But light has another property that is often ignored: polarization. Polarization from stars suffers high cancellation since they are nearly spherical and are spatially unresolved, but rapid rotation breaks that symmetry and produces net polarization. Thus polarization from rotating stars offers complementary information from what has been used to understand them in the past, and the discovery by Gaia of two populations of massive stars, one rapidly rotating and one not, provides new motivation to use polarization to unlock the secrets of rotating stars. This talk will explain the various ways that polarized stellar spectra encode information about the star, and the value of extending that information into the ultraviolet regime.

Date:	Thursday, 30 November 2023
Time:	11:30
Where:	Université de Montréal
	Pavillon MIL A-3561