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They’re a little cagey about exactly where the crossover point lies relative to the likelihood of devastating effects on the planet.
Alt text:
They’re a little cagey about exactly where the crossover point lies relative to the likelihood of devastating effects on the planet.
Wikipedia (Near-Earth Supernova) says that a 25 ly away supernova would wipe out half the ozone layer so that’s probably the lower bound for what we want