Figure 12-14 Cassiopeia A Supernova remnants, such as Cassiopeia A, are typically strong sources of radio waves and X-rays. (a) A radio image produced by the Very Large Array (VLA). (b) A corresponding X-ray picture of Cassiopeia A taken by the Chandra Observatory. The opposing jets of silicon, probably guided by powerful magnetic fields, were ejected early in the supernova, before the iron-rich jets were released. Radiation from the supernova that produced this nebula first reached Earth 300 years ago. The explosion occurred about 11,000 ly from Earth.