A Million-Second Chandra View of Cassiopeia A
  We introduce a million-second observation of the supernova remnant Cassiopeia A with the Chandra X-ray Observatory. The bipolar structure of the Si-rich ejecta (NE jet and SW counterpart) is clearly evident in the new images, and their chemical similarity is confirmed by their spectra. These are most likely due to jets of ejecta as opposed to cavities in the circumstellar medium, since we can reject simple models for the latter. The properties of these jets and the Fe-rich ejecta will provide clues to the explosion of Cas A. 
Una Hwang, J. Martin Laming, Carles Badenes, Fred Berendse, John   Blondin, Denis Cioffi, Tracey DeLaney, Daniel Dewey, Robe...