Holy crap, it has been forever since I posted.  Sorry folks, I am a lazy man.  I’ve been meaning to write this post since I started my new job.

Since October of last year, I have been working as a part-time research assistant at the Radio Astronomy lab at the University of Calgary.  I am basically the odd-jobs guy, writing python scripts and some IDL.  My work is a tiny part of what is done at the CfRA, but the tools we work with, and the science that is being done is DAMN COOL.

The major field we work in is the study of celestial objects via examination of their emissions.  DUH.  That is what astronomy is.  However, the details about what we study are quite interesting.  Rather than focusing on the spectrum of an object, we look at the polarization of the emission.  Polarization can tell us  a lot about both an object and the medium between us and that object.  It is also useful because it allows the study of non-resolved objects (galaxies too distant to see more than a blur).  Polarization of light changes as it passes through an magnetic field.  This phenomenon is called Faraday Rotation.  It basically means that a polarized photon passing through a magnetic field will have the polarization vector rotated (Theta) proportionally to the distance it passes through the field (d), the portion of the field (B) that is parallel to the photon’s motion, and the material that it passes through (nu).

\Theta = \nu (\vec{B} \cdot \vec{d})
This is cool because it means that given a source with an expected polarization angle, a different angle means that the interstellar medium has a magnetic field that can be studied!  The polarization angle can also be used to study the magnetic fields of classes of objects (we focus on the uber-cool active galactic nuclei as well as other types of galaxies).

There is some interesting math involved in the calculation of polarization angles.  There is a wicked system of working with EM polarization called Stokes parameters.  These parameters form a vector composed of the fractional polarizaed intensity (I), the horizontal (Q), vertical (U), and circular (V) polarization.  These allow some nifty and simple calculations.  The relation I have used most frequently is

\Theta = \frac{1}{2}\tan^{-1}{\frac{U}{Q}}

Tada, simple way of turning a fractional horizontal and vertical polarization into a polarization angle.

So, there you have the simple and mundane physics I do.  Next post will include some of the Computer Sciencey stuff I do in order to accomplish Physical Science at CfRA.  Some of the tools I use are open source, so you can download and try them out yourself!