A Supernova Remnant Is the Wreckage, Not the Explosion

One frame, five supernova remnants. NASA's Astronomy Picture of the Day for September 24 shows the debris of five exploded stars in a single field, acquired at the Oukaïmeden Observatory in Morocco with roughly 200 hours of observations and covering a patch of sky equivalent to a thousand full moons tiled together, in the constellation Auriga (the charioteer). The remnants carry catalogue designations rather than names, though one of the five is the Spaghetti Nebula — a fair description of what these objects look like up close. The annotated version also marks an open cluster, M37, and the Tadpole Nebula in the same field. A supernova remnant is the aftermath of the blast, not the blast. As each explosion expanded into space, it created a growing shell of shocked gas and delicate filamentary structures, which is what the picture actually records — hydrogen traced in red, glowing in the wreckage of stars that are no longer there.