Elon Musk, the billionaire founder and CEO of the private spaceflight company SpaceX, wants to help establish a Mars colony of up to 80,000 people by ferrying explorers to the Red Planet for perhaps $500,000 a trip.
(...) we've put all our eggs in one basket. If we were on many worlds and were to mess up down here, there's a way for the human species to continue. I don't for a moment propose that the Earth is a disposable planet, and we have to put enormous efforts into making sure we don't muss up down here. But there is a chance.
Hm, so you're right: http://en.wikipedia.org/wiki/Near-Earth_supernova#Effects_on_Earth In that case, it doesn't sound like that much of a direct threat at all: we can use cheap underground or UV-glass-filtering greenhouses to grow our food. A disaster, but not really an existential threat.