Polarization of Supernovae
My research focuses on the explosion of Type Ia supernovae. I collect the polarization of light over many wavelengths using an observing technique called spectropolarimetry. I then analyze the polarized spectra to determine how much a particular supernova deviates from a perfectly spherical explosion. Any irregularities detected in the spectra can help distinguish among theoretical explosion models or potentially determine what was the progenitor system of the explosion. These are two of the biggest questions we are trying to answer about Type Ia supernovae today.


ISM of external galaxies
I also use the polarization of moderately to heavily extincted Type Ia supernovae to study the interstellar medium (ISM) of galaxies other than our own. Along with the polarization intrinsic to the supernova, our detectors also measure interstellar polarization (ISP). Dust grains aligned in the magnetic field of a galaxy are thought to preferentially absorb light along one of their elongated axes, causing polarization of any light passing through the dust. Through comparison of ISP in the Milky Way and ISP of the host galaxies of the supernovae, we can learn more about the ISM, specifically the dust component, of external galaxies.



Recent publications
Amber L. Porter, Mark D. Leising, G. Grant Williams, et al., "Asymmetries in SN 2014J at Maximum Light Revealed through Spectropolarimetry", The Astrophysical Journal, 2016.

Peter A. Milne, G. Grant Williams, Amber L. Porter, et al., "Multi-epoch Spectropolarimetry of SN 2011fe", Accepted to The Astrophysical Journal, arXiv 1611.07070.