Stories from Physics for 11-14 14-16
A cloud of gas in the Milky Way was observed refracting the radio wave emissions of a distant quasar, to form multiple images of the object. This rare scattering event in 2008-2009 lasted for around 50 days as the gas cloud moved through the line of sight of the quasar.
A. B. Pushkarev, Y. Y. Kovalev, M. L. Lister, T. Hovatta, T. Savolainen, M. F. Aller, M. F., … & W. Max-Moerbeck, VLBA observations of a rare multiple quasar imaging event caused by refraction in the interstellar medium. Astronomy & Astrophysics, vol. 555, 2013, A80.