[RightWhale]

An old supernova would be nothing but a small burnt-out cinder by now, all the dust blown away or condensed into planets and comets. Crab nebula is very recent, just this morning in astronomical time.

[longshadow]

An old supernova would be nothing but a small burnt-out cinder by now, all the dust blown away or condensed into planets and comets.

I suspected that might be the case ....