Milky Way’s magnetic field mapped

Planck telescope records light reflecting off interstellar dust grains

By Christopher Crockett, 11:07 AM May 9, 2014

If the Milky Way were one giant magnet, sprinkling iron filings around it would trace the galaxy’s magnetic field. Scientists have found a more practical way to map the field using the Planck telescope.

To do so, Planck measured the polarization of microwave light that permeates space. When light is polarized, its electric fields all point in the same direction. Light reflecting off interstellar dust grains becomes polarized in the direction the grains are aligned; that direction, in turn, is st...

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