Maybe we can also get an explanation of how the supernova THREATENED THE ENTIRE GALAXY!!!
A hypernova could theoretically be an intense enough radiation emitter to sterilize inhabited planets for several thousand light years around, which would be close enough to "the entire galaxy" as far as the Federation and its neighboring civilizations are concerned. Although we now think a hypernova's radiation would most likely be emitted in two narrow jets from its magnetic poles, rather than spreading out spherically. But it's at least theoretically possible. More so than supernova radiation traveling faster than light, anyway.