A nearby supernova explosion could potentially strip away half of the Earth’s ozone layer, leading to catastrophic consequences. However, scientists have calculated that the nearest potential candidate is 250 light years away, making it extremely unlikely to pose a threat.
A supernova explosion can release powerful X-rays and gamma rays that can break apart molecules in the atmosphere, stripping away the ozone layer. This would expose the Earth to increased ultraviolet radiation from the sun, which could harm photosynthetic microorganisms like algae. The collapse of these ecosystems could lead to mass extinctions.
According to calculations, a star must be within 25-30 light years of the Earth to strip away at least half of the ozone layer. However, there are currently no known supernova candidates in this danger zone. The nearest candidate, Spica, is about 250 light years away and will not reach the danger zone in its lifetime. This makes it highly unlikely that a nearby supernova poses a threat to human civilization.
Source: https://phys.org/news/2025-03-nearby-supernova-mass-extinction.html