SGU Science Picture Of The Week: Milky Way Magnetic Field
What you’re looking at is not a diaphanous, multi-colored, silk flag waving in the wind. It’s the magnetic field of our home galaxy, the Milky Way.
You may be aware that the earth and many other planets in our solar system have magnetic fields…and that the sun does as well. These protective bubbles called magnetospheres act as force fields protecting us from high energy particles that would otherwise wreak havoc on most surface dwellers. Did you know the Milky Way has one as well?
Magnetic fields are not something that we’ve evolved to see directly; we can only see the impact it has on other things and infer its shape. To create the image above, researchers used data collected by the European Space Agency’s Planck satellite which had a treasure trove of information about the polarized light pervading our galaxy.
Light consists of electric and magnetic fields fluctuating at random right angles to each other. Polarized light has all its electric fields vibrating in the same direction. Light in our galaxy often reflects off the innumerable number of interstellar dust grains. When it reflects off of them, the light becomes partially polarized in the direction the grains are aligned. That alignment, in turn, is dictated by the magnetic field in that part of the galaxy. The direction of polarization then allows us to build up an image of the shape of the magnetic field permeating the Milky Way.
Image Credit: (ESA/PLANCK COLLABORATION)