Unfortunately there is no inverse square law for time, only for distance. So if it is large enough, regardless of how long it takes to get to us, we'd be just as toasted. You get sun burns when you are out too long, even though that was so like 8 minutes ago. :-)
That said, it also means we can probably skip that half of galaxy M82 in our search of extraterrestrial intelligence. For the planets that were within a few light years of the supernova, they probably lost anything that wasn't bolted down in terms of atmospheric gases :-).
That said, it also means we can probably skip that half of galaxy M82 in our search of extraterrestrial intelligence. For the planets that were within a few light years of the supernova, they probably lost anything that wasn't bolted down in terms of atmospheric gases :-).