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. These objects can be dated by measuring the decay of titanium-44 in them. These objects are believed to be the 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. (-5[2])One of these objects (-5[1])is the brightest extrasolar radio source in the night sky; that object is Cas (-5[1])A. A pulsar is located at the center of one of these objects that forms the Crab Nebula. (-5[1])For 10 points, (10[1])name these clouds of heated interstellar gas left behind by massive stellar explosions. ■END■ (10[1]0[3])