During the not-actually-adiabatic “adiabatic phase” of these objects, the expression for their temperature contains a factor written E51 (“E-sub-51”) and is proportional to time to the negative 6/5ths. A transition during the evolution of these structures occurs when the sweep-up mass exceeds the ejecta mass. Diffusive shock acceleration within these objects are the probable primary source of “below-the-knee” cosmic rays. These objects are morphologically classified as shell-type, mixed morphology-type, or (*) plerions, the last of which consists of one of these objects excited by the winds of a central pulsar. One of these objects is the brightest extrasolar radio source in the night sky; that object (-5[1])is Cas A. A pulsar is located at the center of one of these objects that forms the Crab Nebula. For 10 points, name these clouds of heated interstellar (10[1])gas (-5[1])left behind by massive stellar explosions. ■END■ (10[1]0[2])